Arc'teryx Atom SL vs Proton FL: For chilly summer mornings

UPDATE: The Proton FL is now called the Proton SL Hoody. Arc'teryx released the 2025 version in March, and our initial impression is that the Proton SL is a fantastic insulated and highly breathable layer for medium- to high-output activities (or just for wearing around town).

Also be sure to check out our most up to date and in-depth comparison of the Arc'teryx Atom SL (formerly the Atom Lightweight) vs the Proton SL Hoody.

Proton FL.

Now that the summer is here, let's take a look at how the differences between Proton FL vs Atom SL play out.

Atom SL (Super Light) and Proton FL (Fast & Light) are the two most breathable, least warm alternatives you can find in Arc'teryx's insulated jacket line-up.

They're both best suited for chilly summer and/or spring mornings, followed by a high output activity (primarily rock / alpine climbing).

These jackets are more alike than they're different.

Proton Lightweight (FL) is a bit more durable, a bit more comfortable and is an inch longer
Atom SL is a bit more breathable

Warmth

Neither of these jackets will provide substantial warmth. Like I clarified earlier, they aren't even designed to do so anyway.

Proton FL is insulated with Octa Loft throughout the entire jacket. The Atom SL, on the other hand, is insulated with Coreloft Compact only around the core, which holds it warmth back.

I'd recommend you to take a look at the lowest temperatures they're expected to be worn comfortably by an average person (both are positioned at the bottom):

Temperature ratings of Arc'teryx jackets

Name	Est. Temp (F/C)	Breathability	Wind Res.	Abrasion res.	Packability	Best pick for	Review	Pit venting?	Two way zipper?	Stuffs into itself?	Type	Fill Power (in3/oz)	Fill Weight (g)	Fill Volume (in3)	Synthetic Fill	Synth. Fill Weight	Face Fabric	Activity	Fit	Weight	Length (CB)	Discontinued?	atomproton	nucleiproton	bestsyntheticjackets	Internal pockets	External pockets	bestdownjackets	sentences
Arc'teryx Alpha Parka (Men's - Women's)	-18/-28	No data	No data	No data	No data	Warmest Arc'teryx jacket.	Review	No	Yes	Yes	Down	850	296	8,875	Coreloft	90 g/m²	N30r 2L GoreTex Infinium	Climbing	Regular	805 g / 1 lb 12.4 oz	86 cm / 34 in	No						bestdownjackets	Fill weight of Arc'teryx Alpha Parka (Men's - Women's) is 296 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 8875 cubic inches of down fill volume. It's also reinforced with 90 g/m² of Coreloft.
Arc'teryx Alpha Lightweight (Men's - Women's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	850	117	3,508	Coreloft Compact	40 g/m²	Hadron 2L Gore-Tex Infinium	Climbing	Regular	540 g / 1 lb 3 oz	79.5 cm / 31.25 in	No						bestdownjackets	Fill weight of Arc'teryx Alpha Lightweight (Men's - Women's) is 117 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3508 cubic inches of down fill volume. It's also reinforced with 40 g/m² of Coreloft Compact.
Arc'teryx Atom (aka LT) ( Men's - Women's)	43/6	9/10	6/10	7/10	5/10	High output activities.	Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Continuous	60 g/m²	20D Tyono	All Round	Trim	375 g / 13.2 oz	74 cm / 29.1 in	No	atomproton		bestsyntheticjackets	1x chest	-		Arc'teryx Atom (aka LT) ( Men's - Women's) is equipped with 60 g/m² of Coreloft Continuous.
Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's)	18/-8	4/10	8/10	8/10	3/10		Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Continuous	120 g/m2 + 80 g/m2 + 60 g/m2	30D Tyono	All Round	Regular	475 g / 1 lb	74 cm / 29.1 in	No	atomproton		bestsyntheticjackets	1x chest	-		Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's) is equipped with 120 g/m2 + 80 g/m2 + 60 g/m2 of Coreloft Continuous.
Arc'teryx Atom Lightweight (aka SL) (Men's - Women's)	52/11	10/10	2/10	7/10	6/10		Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Compact	40 g/m²	20D Tyono	All Round	Trim	270 g / 9.5 oz	72 cm / 28.3 in	No	atomproton		bestsyntheticjackets	-	-		Arc'teryx Atom Lightweight (aka SL) (Men's - Women's) is equipped with 40 g/m² of Coreloft Compact.
Arc'teryx Beta Down Insulated (Men's)	0/-18	No data	No data	No data	No data			Yes	Yes	No	Parka	850	126	3,778	Coreloft	80 g/m²	2L 40D Gore-Tex	All Round	Regular	760 g / 1 lb 10.8 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Arc'teryx Beta Down Insulated (Men's) is 126 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume. It's also reinforced with 80 g/m² of Coreloft.
Arc'teryx Beta Insulated (Men's)	21/-6	No data	No data	No data	No data		Review	Yes, zips	Yes	No	Parka	N/A	N/A	N/A	Coreloft Continuous	80 g/m²	2L 40D Gore-Tex	All Round	Regular	680 g / 1 lb 8 oz	78.5 cm / 31 in	No						bestdownjackets	Arc'teryx Beta Insulated (Men's) is equipped with 80 g/m² of Coreloft Continuous.
Arc'teryx Beta Insulated Coat (Women's)	16/-9	No data	No data	No data	Testing		Review	No	Yes	No	Parka	N/A	N/A	N/A	Coreloft	80 g/m² + 120 g/m²	2L 40D Gore-Tex	Around Town	Regular	600 g / 1 lb 5.2 oz	86 cm / 34 in	No						bestdownjackets	Arc'teryx Beta Insulated Coat (Women's) is equipped with 80 g/m² + 120 g/m² of Coreloft .
Arc'teryx Cerium (aka LT) (Men's - Women's)	26/-3	No data	No data	No data	No data	Light down jacket.	Review	No	No	Yes	Down	850	113	3,388	Coreloft	80 + 100 g/m²	Arato 15	All Round	Trim	335 g / 11.8 oz	72 cm / 28.3 in	No						bestdownjackets	Fill weight of Arc'teryx Cerium (aka LT) (Men's - Women's) is 113 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3388 cubic inches of down fill volume. It's also reinforced with 80 + 100 g/m² of Coreloft.
Arc'teryx Cerium Hybrid (Women's)	44/7	No data	No data	No data	No data			No	No	Yes	Down	850	44	1,319	Coreloft	40 + 100 g/m²	Arato 15 + Fortius Air 50	All Round	Trim	260 g / 9.2 oz	70 cm / 27.5 in	No						bestdownjackets	#REF!
Arc'teryx Coelle (Women's)	14/-10	No data	No data	No data	No data			No	Yes	No	Parka	N/A	N/A	N/A	Coreloft	98 g/m²	40D 2L Gore-Tex	Around Town	Regular	435g / 15.3 oz	70 cm / 27.5 in	No							Arc'teryx Cerium Hybrid (Women's) is equipped with 98 g/m² of Coreloft.
Arc'teryx Liatris (Women's)	5/-15	No data	No data	No data	No data			No	No	No	Parka	850	93	2,788	Climashield	80 g/m2 + 60 g/m2	70D 3L Gore-Tex	Around Town	Regular	890 g / 1 lb 15.4 oz	75 cm / 29.5 in	No							Fill weight of Arc'teryx Liatris (Women's) is 93 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 2788 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
Arc'teryx Liatris Parka (Women's)	2/-17	No data	No data	No data	No data			No	No	No	Parka	850	136	4,078	Climashield	80 g/m2 + 60 g/m2	70D 3L Gore-Tex	Around Town	Regular	1.093 kg / 2 lb 6.6 oz	109 cm / 43 in	No							Fill weight of Arc'teryx Liatris Parka (Women's) is 136 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 4078 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
Arc'teryx Nuclei (aka FL) ( Men's - Women's)	32/0	2/10	9/10	2/10	10/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	Coreloft Continuous	65 g/m²	Arato 10r	All Round	Regular	325 g / 11.5 oz	75 cm / 29.5 in	No		nucleiproton	bestsyntheticjackets	2x dump	-		Arc'teryx Nuclei (aka FL) ( Men's - Women's) is equipped with 65 g/m² of Coreloft Continuous.
Arc'teryx Nuclei SV (Women's)	5/-15	1/10	10/10	2/10	8/10	Warmest belay jacket.	Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	Coreloft Continuous	190 g/m2 + 90 g/m2	Arato 15	All Round	Regular	600 g / 1 lb 5.2 oz	81 cm / 31.8 in	No		nucleiproton	bestsyntheticjackets	2x dump	1x chest		Arc'teryx Nuclei SV (Women's) is equipped with 190 g/m2 + 90 g/m2 of Coreloft Continuous.
Arc'teryx Patera (Women's)	21/-6	No data	No data	No data	No data		Review	No	Yes	No	Parka	750	67	1,773	Coreloft	60 + 80 g/m²	2L Gore-Tex	Around Town	Trim	867 g / 1 lb 14.6 oz	99 cm / 39 in	No							Fill weight of Arc'teryx Patera (Women's) is 67 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 1773 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Patera Long (Women's)	0/-18	No data	No data	No data	No data	Women's warmest parka.		No	Yes	No	Parka	750	204	5,397	Coreloft	60 + 80 g/m²	2L Gore-Tex	Around Town	Regular	1.1 kg / 2 lb 6.8 oz	117.5 cm / 46.25 in	No							Fill weight of Arc'teryx Patera Long (Women's) is 204 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5397 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Proton Lightweight (aka FL) (Men's - Women's)	48/9	8/10	4/10	7/10	6/10	Chilly summer mornings.	Review	No	No	No	Synthetic	N/A	N/A	N/A	Octa Loft	94 g/m²	Fortius Air 20	Climbing	Trim	343 g / 12.1 oz	75 cm / 29.5 in	No	atomproton	nucleiproton	bestsyntheticjackets	-	1x chest		Arc'teryx Proton Lightweight (aka FL) (Men's - Women's) is equipped with 94 g/m² of Octa Loft.
Arc'teryx Therme Parka (Men's)	5/-15	No data	No data	No data	No data		Review	No	Yes	No	Parka	750	120	3,175	Coreloft	60 + 80 g/m²	P75d Polyester	Around Town	Regular	991 g / 2 lb 3 oz	85 cm / 33.5 in	No							Fill weight of Arc'teryx Therme Parka (Men's) is 120 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3175 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Therme SV (Men's)	-11/-24	No data	No data	No data	No data	Men's warmest parka.	Review	No	Yes	No	Parka	750	211	5,582	Coreloft	60 g/m²	2L Gore-Tex	Around Town	Regular	1.072 kg / 2 lb 5.8 oz	96 cm / 37.75 in	No							Fill weight of Arc'teryx Therme SV (Men's) is 211 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5582 cubic inches of down fill volume. It's also reinforced with 60 g/m² of Coreloft.
Arc'teryx Thorium ( Men's - Women's)	12/-11	No data	No data	No data	No data	Warm down jacket.	Review	No	Yes	Yes	Down	750	140	3,704	Coreloft	80 + 140 g/m²	Arato 30	All Round	Regular	517 g / 1 lb 2.2 oz	71.5 cm / 28.1 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium ( Men's - Women's) is 140 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3704 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium Parka (Women's)	-2/-19	No data	No data	No data	No data		Review	No	Yes	No	Down	750	209	5,529	Coreloft	80 + 140 g/m²	Arato 20	Around Town	Regular	610 g / 1 lb 5.5 oz	115.8 cm / 45.6 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium Parka (Women's) is 209 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5529 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium SV (Men's)	3/-16	No data	No data	No data	No data	Gore-Tex down jacket.		No	Yes	Yes	Down	750	169	4,471	Coreloft	80 + 140 g/m²	Arato 30 & 2L Gore-Tex Infinium	Around Town	Regular	645 g / 1 lb 6.8 oz	73 cm / 28.75 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium SV (Men's) is 169 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 4471 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium SV Parka (Men's)	0/-18	No data	No data	No data	No data			No	Yes	No	Down	750	195	5,159	Coreloft	80 + 140 g/m²	Arato 30 & 2L Gore-Tex Infinium	Around Town	Regular	685 g / 1 lb 8.2 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium SV Parka (Men's) is 195 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5159 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Black Diamond Access Down (Men's - Women's)	7/-14	No data	No data	No data	No data			No	Yes	Yes	Down	700	155	3,827	N/A	N/A	30D ripstop nylon	All Round	Regular	442 g / 15.6 oz	76 cm / 29.75 in	No						bestdownjackets	Fill weight of Black Diamond Access Down (Men's - Women's) is 155 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3827 cubic inches of down fill volume.
Feathered Friends Eos(Men's - Women's)	8/-13	No data	No data	No data	No data			No	No	Yes	Down	900	105	3,333	N/A	N/A	Pertex Quantum	All Round	Regular	306 g / 10.8 oz	?	No						bestdownjackets	Fill weight of Feathered Friends Eos(Men's - Women's) is 105 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 3333 cubic inches of down fill volume.
Feathered Friends Khumbu (Men's)	-17/-27	No data	No data	No data	No data			No	No	Yes	Down	900	378	12,000	Primaloft Gold	200 g	Pretex Shield XT	All Round	Regular	960 g / 2 lb 2 oz	?	No						bestdownjackets	Fill weight of Feathered Friends Khumbu (Men's) is 378 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 12000 cubic inches of down fill volume. It's also reinforced with 200 g of Primaloft Gold.
Mountain Equipment Exo (Men's)	-10/-23	No data	No data	No data	No data			No	Yes	Yes	Down	800	265	7,478	N/A	N/A	Nylon	All Round	Regular	770 g / 1 lb 11.2 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Mountain Equipment Exo (Men's) is 265 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 7478 cubic inches of down fill volume.
Mountain Equipment K7 (Men's)	-13/-25	No data	No data	No data	No data			No	Yes	Yes	Down	800	300	8,466	N/A	N/A	30D Drilite	All Round	Regular	820 g / 1 lb 13 oz	76 cm / 30 in	No						bestdownjackets	Fill weight of Mountain Equipment K7 (Men's) is 300 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8466 cubic inches of down fill volume.
Mountain Hardwear GW/2 (Men's - Women's)	28/-2	No data	No data	No data	No data			No	No	Yes	Down	800	85	2,399	N/A	N/A	10D Ripstop Nylon	All Round	Trim	250 g / 8.8 oz	70 cm / 27.5 in	No						bestdownjackets	Fill weight of Mountain Hardwear GW/2 (Men's - Women's) is 85 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 2399 cubic inches of down fill volume.
Outdoor Research Sup. Alp. (Men's - Women's)	3/-16	No data	No data	No data	No data			No	Yes	No	Down	800	182	5,136	N/A	N/A	30D Pertex Quantum Pro	All Round	Regular	825 g / 1 lb 13.1 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Outdoor Research Sup. Alp. (Men's - Women's) is 182 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5136 cubic inches of down fill volume.
Patagonia AlpLight (Men's - Women's)	36/2	No data	No data	No data	No data			No	No	Yes	Down	800	100	2,822	N/A	N/A	0.8 oz 10D polyester	All Round	Slim	270 g / 9.5 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia AlpLight (Men's - Women's) is 100 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 2822 cubic inches of down fill volume.
Patagonia AlpLoft (Men's)	-10/-23	No data	No data	No data	No data			No	Yes	Yes	Down	800	295	8,325	N/A	N/A	Pertex Quantom	All Round	Regular	680 g / 1 lb 8 oz	81 cm / 31.8 in	No						bestdownjackets	Fill weight of Patagonia AlpLoft (Men's) is 295 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8325 cubic inches of down fill volume.
Patagonia DAS (Men's - Women's)	10/-12	1/10	9/10	3/10	6/10		Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	PrimaLoft Gold Insulation Eco	133 + 40 g	Pertex Quantum Pro	All Round	Regular	555 g / 1 lb 3.6 oz	84 cm / 33 in	No			bestsyntheticjackets	2x dump	1x chest		Patagonia DAS (Men's - Women's) is equipped with 133 + 40 g of PrimaLoft Gold Insulation Eco.
Patagonia DAS Light(Men's)	34/1	2/10	8/10	2/10	9/10		Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	PlumaFill	65 g	10D Pertex Quantum Pro	All Round	Regular	320 g / 11.3 oz	77 cm / 30.5 in	No			bestsyntheticjackets	-	1x chest		Patagonia DAS Light(Men's) is equipped with 65 g of PlumaFill.
Patagonia Down Sweater (Men's - Women's)	23/-5	No data	4/10	6/10	7/10		Review	No	No	Yes	Down	800	150	4,233	N/A	N/A	1.4 oz 20x30D polyester	All Round	Regular	428 g / 15.1 oz	67 cm / 26.25 in	No						bestdownjackets	Fill weight of Patagonia Down Sweater (Men's - Women's) is 150 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 4233 cubic inches of down fill volume.
Patagonia Downdrift (Men's - Women's)	18/-8	No data	No data	No data	No data			No	No	No	Down	600	279	5,905	N/A	N/A	4.2 oz polyester	Around Town	Regular	1.014 kg / 2 lb 3.8 oz	?	No						bestdownjackets	Fill weight of Patagonia Downdrift (Men's - Women's) is 279 grams. Its fill power is 600 cubic inches per ounce, which equals to a total of 5905 cubic inches of down fill volume.
Patagonia Fitz Roy (Men's - Women's)	14/-10	No data	No data	No data	No data			No	No	Yes	Down	800	128	3,612	N/A	N/A	20D Nylon	All Round	Regular	632 g / 1lb 6.3 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia Fitz Roy (Men's - Women's) is 128 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 3612 cubic inches of down fill volume.
Patagonia Isthmus (Men's)	36/2	No data	No data	No data	No data			No	No	No	Parka	N/A	N/A	N/A	ThermoGreen	60 g	4.2 oz polyester	Around Town	Regular	895 g / 1 lb 15.6 oz	70 cm / 27.5 in	No							Patagonia Isthmus (Men's) is equipped with 60 g of ThermoGreen.
Patagonia Jackson Glacier (Men's - Women's)	12/-11	No data	No data	No data	No data		Review	No	Yes	No	Down	700	141	3,482	N/A	N/A	3.6 oz 50D polyester	Around Town	Regular	880 g / 1 lb 15 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Patagonia Jackson Glacier (Men's - Women's) is 141 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3482 cubic inches of down fill volume.
Patagonia Jackson Glacier Parks ( Women's)	7/-14	No data	No data	No data	No data			No	No	No	Parka	700	218	5,383	N/A	N/A	50D Polyester	Around Town	Regular	1.142 kg / 2 lb 8.3 oz	?	No							Fill weight of Patagonia Jackson Glacier Parks ( Women's) is 218 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 5383 cubic inches of down fill volume.
Patagonia Micro Puff (Men's - Women's)	37/3	5/10	6/10	5/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	PlumaFill	65 g	Pertex Quantum	All Round	Regular	298 g / 10.5 oz	75 cm / 29.5 in	No			bestsyntheticjackets	2x dump	-		Patagonia Micro Puff (Men's - Women's) is equipped with 65 g of PlumaFill.
Patagonia Nano Air (Men's - Women's)	39/4	7/10	5/10	5/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	FullRange	60 g	33D nylon ripstop	All Round	Trim	401 g / 14.14 oz	?	No			bestsyntheticjackets	-	2x chest		Patagonia Nano Air (Men's - Women's) is equipped with 60 g of FullRange.
Patagonia Nano Air Light Hybrid (Men's - Women's)	50/10	No data	No data	No data	No data			No	No	No	Synthetic	N/A	N/A	N/A	FullRange	40 g	20D nylon ripstop	All Round	Trim	335 g / 11.8 oz	?	No							Patagonia Nano Air Light Hybrid (Men's - Women's) is equipped with 40 g of FullRange.
Patagonia Nano Puff (Men's - Women's)	41/5	4/10	6/10	6/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	PrimaLoft Gold Insulation Eco	60 g	22D Polyester	All Round	Regular	363 g / 12.8 oz	71.5 cm / 28 in	No			bestsyntheticjackets	1x chest	-		Patagonia Nano Puff (Men's - Women's) is equipped with 60 g of PrimaLoft Gold Insulation Eco.
Patagonia Silent Down (Men's - Women's)	26/-3	No data	No data	No data	No data		Review	No	No	No	Down	700	109	2,691	N/A	N/A	2.2 oz polyester	Around Town	Regular	585 g / 1 lb 4.7 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia Silent Down (Men's - Women's) is 109 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2691 cubic inches of down fill volume.
Patagonia Stormshadow (Men's)	0/-18	No data	No data	No data	No data			No	No	No	Parka	700	259	6,395	N/A	N/A	75D Polyester	Around Town	Regular	1.182 kg / 2 lb 9.7 oz	?	No							Fill weight of Patagonia Stormshadow (Men's) is 259 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 6395 cubic inches of down fill volume.
Patagonia Tres 3-in-1Patagonia Tres 3-in-1 (Men's - Women's)	8/-13	No data	No data	No data	No data		Review	No	No	No	Parka	700	118	2,914	N/A	N/A	5.5 oz polyester	Around Town	Regular	1.307 kg / 2 lb 14.1 oz	85 cm / 33.5 in	No							Fill weight of Patagonia Tres 3-in-1Patagonia Tres 3-in-1 (Men's - Women's) is 118 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2914 cubic inches of down fill volume.
Patagonia Vosque 3-in-1 (Women's)	10/-12	No data	No data	No data	No data		Review	No	No	No	Parka	N/A	N/A	N/A	ThermoLite	100 g	65% nylon, 35% polyester	Around Town	Regular	1.360 kg / 3 lb	90 cm / 35.5 in	No							Patagonia Vosque 3-in-1 (Women's) is equipped with 100 g of ThermoLite.
Rab Electron Pro (Men's - Women's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	800	180	5,079	N/A	N/A	20D Pertex Quantum Pro	All Round	Regular	525 g / 1 lb 2.5 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Rab Electron Pro (Men's - Women's) is 180 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5079 cubic inches of down fill volume.
Rab Infinity Alpine (Men's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	800	175	4,938	N/A	N/A	30D & 13D Gore-Tex Infinium	All Round	Regular	551 g / 1 lb 3.4 oz	76.5 cm / 30.1 in	No						bestdownjackets	Fill weight of Rab Infinity Alpine (Men's) is 175 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 4938 cubic inches of down fill volume.
Rab Infinity Microlight (Men's - Women's)	19/-7	No data	No data	No data	No data			No	No	Yes	Down	700	146	3,605	N/A	N/A	13D Gore-Tex Infinium	All Round	Regular	452 g / 15.9 oz	74 cm / 29.1 in	No						bestdownjackets	Fill weight of Rab Infinity Microlight (Men's - Women's) is 146 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3605 cubic inches of down fill volume.
Rab Microlight Alpine (Men's - Women's)	7/-14	No data	No data	No data	No data			No	No	Yes	Down	700	153	3,778	N/A	N/A	30D Pertex Quantum	All Round	Regular	466 g / 1 lb 0.5 oz	72 cm / 28.5 in	No						bestdownjackets	Fill weight of Rab Microlight Alpine (Men's - Women's) is 153 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume.
Rab Neutrino Pro (Men's - Women's)	-2/-19	No data	No data	No data	No data			No	Yes	Yes	Down	800	212	5,982	N/A	N/A	20D Pertex Quantum Pro	All Round	Regular	585 g / 1 lb 8.6 oz	77 cm / 30.3 in	No						bestdownjackets	Fill weight of Rab Neutrino Pro (Men's - Women's) is 212 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5982 cubic inches of down fill volume.
Rab Positron Pro (Men's)	-13/-25	No data	No data	No data	No data			No	Yes	Yes	Down	800	300	8,466	N/A	N/A	40D Pertex Quantum Pro	All Round	Regular	740 g / 1 lb 10 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Rab Positron Pro (Men's) is 300 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8466 cubic inches of down fill volume.
REI Magma 850 Hoodie 2.0 (Men's - Women's)	14/-10	No data	No data	No data	No data			No	No	Yes	Down	850	120	3,598	N/A	N/A	Pertex mini ripstop nylon	All Round	Regular	340 g / 13.75 oz	74 cm / 29.25 in	No						bestdownjackets	Fill weight of REI Magma 850 Hoodie 2.0 (Men's - Women's) is 120 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3598 cubic inches of down fill volume.

Assumptions: Worn over a thin shirt, no output, no precipitation, light to no wind. Values are always for size M and for men's, except for women's-only items.

Primary use of this spectrum is for comparison, rather than figuring out absolute temp ratings.

Working principles of insulated jackets: https://outdoorcrunch.com/jackets/
CLO Values: https://outdoorcrunch.com/clo-values/
Best Arc'teryx jackets: https://outdoorcrunch.com/best-arcteryx-jacket/
Best sellers (new pages)
- https://arcteryx.com/us/en/c/mens/p/best-sellers
- https://arcteryx.com/us/en/c/womens/p/best-sellers

Performance ratings of Arc'teryx synthetics

Name	Est. Temp (F/C)	Breathability	Wind Res.	Abrasion res.	Packability	Best pick for	Review	Pit venting?	Two way zipper?	Stuffs into itself?	Type	Fill Power (in3/oz)	Fill Weight (g)	Fill Volume (in3)	Synthetic Fill	Synth. Fill Weight	Face Fabric	Activity	Fit	Weight	Length (CB)	Discontinued?	atomproton	nucleiproton	bestsyntheticjackets	Internal pockets	External pockets	bestdownjackets	sentences
Arc'teryx Alpha Parka (Men's - Women's)	-18/-28	No data	No data	No data	No data	Warmest Arc'teryx jacket.	Review	No	Yes	Yes	Down	850	296	8,875	Coreloft	90 g/m²	N30r 2L GoreTex Infinium	Climbing	Regular	805 g / 1 lb 12.4 oz	86 cm / 34 in	No						bestdownjackets	Fill weight of Arc'teryx Alpha Parka (Men's - Women's) is 296 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 8875 cubic inches of down fill volume. It's also reinforced with 90 g/m² of Coreloft.
Arc'teryx Alpha Lightweight (Men's - Women's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	850	117	3,508	Coreloft Compact	40 g/m²	Hadron 2L Gore-Tex Infinium	Climbing	Regular	540 g / 1 lb 3 oz	79.5 cm / 31.25 in	No						bestdownjackets	Fill weight of Arc'teryx Alpha Lightweight (Men's - Women's) is 117 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3508 cubic inches of down fill volume. It's also reinforced with 40 g/m² of Coreloft Compact.
Arc'teryx Atom (aka LT) ( Men's - Women's)	43/6	9/10	6/10	7/10	5/10	High output activities.	Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Continuous	60 g/m²	20D Tyono	All Round	Trim	375 g / 13.2 oz	74 cm / 29.1 in	No	atomproton		bestsyntheticjackets	1x chest	-		Arc'teryx Atom (aka LT) ( Men's - Women's) is equipped with 60 g/m² of Coreloft Continuous.
Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's)	18/-8	4/10	8/10	8/10	3/10		Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Continuous	120 g/m2 + 80 g/m2 + 60 g/m2	30D Tyono	All Round	Regular	475 g / 1 lb	74 cm / 29.1 in	No	atomproton		bestsyntheticjackets	1x chest	-		Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's) is equipped with 120 g/m2 + 80 g/m2 + 60 g/m2 of Coreloft Continuous.
Arc'teryx Atom Lightweight (aka SL) (Men's - Women's)	52/11	10/10	2/10	7/10	6/10		Review	Yes, mesh	No	No	Synthetic	N/A	N/A	N/A	Coreloft Compact	40 g/m²	20D Tyono	All Round	Trim	270 g / 9.5 oz	72 cm / 28.3 in	No	atomproton		bestsyntheticjackets	-	-		Arc'teryx Atom Lightweight (aka SL) (Men's - Women's) is equipped with 40 g/m² of Coreloft Compact.
Arc'teryx Beta Down Insulated (Men's)	0/-18	No data	No data	No data	No data			Yes	Yes	No	Parka	850	126	3,778	Coreloft	80 g/m²	2L 40D Gore-Tex	All Round	Regular	760 g / 1 lb 10.8 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Arc'teryx Beta Down Insulated (Men's) is 126 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume. It's also reinforced with 80 g/m² of Coreloft.
Arc'teryx Beta Insulated (Men's)	21/-6	No data	No data	No data	No data		Review	Yes, zips	Yes	No	Parka	N/A	N/A	N/A	Coreloft Continuous	80 g/m²	2L 40D Gore-Tex	All Round	Regular	680 g / 1 lb 8 oz	78.5 cm / 31 in	No						bestdownjackets	Arc'teryx Beta Insulated (Men's) is equipped with 80 g/m² of Coreloft Continuous.
Arc'teryx Beta Insulated Coat (Women's)	16/-9	No data	No data	No data	Testing		Review	No	Yes	No	Parka	N/A	N/A	N/A	Coreloft	80 g/m² + 120 g/m²	2L 40D Gore-Tex	Around Town	Regular	600 g / 1 lb 5.2 oz	86 cm / 34 in	No						bestdownjackets	Arc'teryx Beta Insulated Coat (Women's) is equipped with 80 g/m² + 120 g/m² of Coreloft .
Arc'teryx Cerium (aka LT) (Men's - Women's)	26/-3	No data	No data	No data	No data	Light down jacket.	Review	No	No	Yes	Down	850	113	3,388	Coreloft	80 + 100 g/m²	Arato 15	All Round	Trim	335 g / 11.8 oz	72 cm / 28.3 in	No						bestdownjackets	Fill weight of Arc'teryx Cerium (aka LT) (Men's - Women's) is 113 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3388 cubic inches of down fill volume. It's also reinforced with 80 + 100 g/m² of Coreloft.
Arc'teryx Cerium Hybrid (Women's)	44/7	No data	No data	No data	No data			No	No	Yes	Down	850	44	1,319	Coreloft	40 + 100 g/m²	Arato 15 + Fortius Air 50	All Round	Trim	260 g / 9.2 oz	70 cm / 27.5 in	No						bestdownjackets	#REF!
Arc'teryx Coelle (Women's)	14/-10	No data	No data	No data	No data			No	Yes	No	Parka	N/A	N/A	N/A	Coreloft	98 g/m²	40D 2L Gore-Tex	Around Town	Regular	435g / 15.3 oz	70 cm / 27.5 in	No							Arc'teryx Cerium Hybrid (Women's) is equipped with 98 g/m² of Coreloft.
Arc'teryx Liatris (Women's)	5/-15	No data	No data	No data	No data			No	No	No	Parka	850	93	2,788	Climashield	80 g/m2 + 60 g/m2	70D 3L Gore-Tex	Around Town	Regular	890 g / 1 lb 15.4 oz	75 cm / 29.5 in	No							Fill weight of Arc'teryx Liatris (Women's) is 93 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 2788 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
Arc'teryx Liatris Parka (Women's)	2/-17	No data	No data	No data	No data			No	No	No	Parka	850	136	4,078	Climashield	80 g/m2 + 60 g/m2	70D 3L Gore-Tex	Around Town	Regular	1.093 kg / 2 lb 6.6 oz	109 cm / 43 in	No							Fill weight of Arc'teryx Liatris Parka (Women's) is 136 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 4078 cubic inches of down fill volume. It's also reinforced with 80 g/m2 + 60 g/m2 of Climashield.
Arc'teryx Nuclei (aka FL) ( Men's - Women's)	32/0	2/10	9/10	2/10	10/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	Coreloft Continuous	65 g/m²	Arato 10r	All Round	Regular	325 g / 11.5 oz	75 cm / 29.5 in	No		nucleiproton	bestsyntheticjackets	2x dump	-		Arc'teryx Nuclei (aka FL) ( Men's - Women's) is equipped with 65 g/m² of Coreloft Continuous.
Arc'teryx Nuclei SV (Women's)	5/-15	1/10	10/10	2/10	8/10	Warmest belay jacket.	Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	Coreloft Continuous	190 g/m2 + 90 g/m2	Arato 15	All Round	Regular	600 g / 1 lb 5.2 oz	81 cm / 31.8 in	No		nucleiproton	bestsyntheticjackets	2x dump	1x chest		Arc'teryx Nuclei SV (Women's) is equipped with 190 g/m2 + 90 g/m2 of Coreloft Continuous.
Arc'teryx Patera (Women's)	21/-6	No data	No data	No data	No data		Review	No	Yes	No	Parka	750	67	1,773	Coreloft	60 + 80 g/m²	2L Gore-Tex	Around Town	Trim	867 g / 1 lb 14.6 oz	99 cm / 39 in	No							Fill weight of Arc'teryx Patera (Women's) is 67 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 1773 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Patera Long (Women's)	0/-18	No data	No data	No data	No data	Women's warmest parka.		No	Yes	No	Parka	750	204	5,397	Coreloft	60 + 80 g/m²	2L Gore-Tex	Around Town	Regular	1.1 kg / 2 lb 6.8 oz	117.5 cm / 46.25 in	No							Fill weight of Arc'teryx Patera Long (Women's) is 204 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5397 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Proton Lightweight (aka FL) (Men's - Women's)	48/9	8/10	4/10	7/10	6/10	Chilly summer mornings.	Review	No	No	No	Synthetic	N/A	N/A	N/A	Octa Loft	94 g/m²	Fortius Air 20	Climbing	Trim	343 g / 12.1 oz	75 cm / 29.5 in	No	atomproton	nucleiproton	bestsyntheticjackets	-	1x chest		Arc'teryx Proton Lightweight (aka FL) (Men's - Women's) is equipped with 94 g/m² of Octa Loft.
Arc'teryx Therme Parka (Men's)	5/-15	No data	No data	No data	No data		Review	No	Yes	No	Parka	750	120	3,175	Coreloft	60 + 80 g/m²	P75d Polyester	Around Town	Regular	991 g / 2 lb 3 oz	85 cm / 33.5 in	No							Fill weight of Arc'teryx Therme Parka (Men's) is 120 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3175 cubic inches of down fill volume. It's also reinforced with 60 + 80 g/m² of Coreloft.
Arc'teryx Therme SV (Men's)	-11/-24	No data	No data	No data	No data	Men's warmest parka.	Review	No	Yes	No	Parka	750	211	5,582	Coreloft	60 g/m²	2L Gore-Tex	Around Town	Regular	1.072 kg / 2 lb 5.8 oz	96 cm / 37.75 in	No							Fill weight of Arc'teryx Therme SV (Men's) is 211 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5582 cubic inches of down fill volume. It's also reinforced with 60 g/m² of Coreloft.
Arc'teryx Thorium ( Men's - Women's)	12/-11	No data	No data	No data	No data	Warm down jacket.	Review	No	Yes	Yes	Down	750	140	3,704	Coreloft	80 + 140 g/m²	Arato 30	All Round	Regular	517 g / 1 lb 2.2 oz	71.5 cm / 28.1 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium ( Men's - Women's) is 140 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 3704 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium Parka (Women's)	-2/-19	No data	No data	No data	No data		Review	No	Yes	No	Down	750	209	5,529	Coreloft	80 + 140 g/m²	Arato 20	Around Town	Regular	610 g / 1 lb 5.5 oz	115.8 cm / 45.6 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium Parka (Women's) is 209 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5529 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium SV (Men's)	3/-16	No data	No data	No data	No data	Gore-Tex down jacket.		No	Yes	Yes	Down	750	169	4,471	Coreloft	80 + 140 g/m²	Arato 30 & 2L Gore-Tex Infinium	Around Town	Regular	645 g / 1 lb 6.8 oz	73 cm / 28.75 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium SV (Men's) is 169 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 4471 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Arc'teryx Thorium SV Parka (Men's)	0/-18	No data	No data	No data	No data			No	Yes	No	Down	750	195	5,159	Coreloft	80 + 140 g/m²	Arato 30 & 2L Gore-Tex Infinium	Around Town	Regular	685 g / 1 lb 8.2 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Arc'teryx Thorium SV Parka (Men's) is 195 grams. Its fill power is 750 cubic inches per ounce, which equals to a total of 5159 cubic inches of down fill volume. It's also reinforced with 80 + 140 g/m² of Coreloft.
Black Diamond Access Down (Men's - Women's)	7/-14	No data	No data	No data	No data			No	Yes	Yes	Down	700	155	3,827	N/A	N/A	30D ripstop nylon	All Round	Regular	442 g / 15.6 oz	76 cm / 29.75 in	No						bestdownjackets	Fill weight of Black Diamond Access Down (Men's - Women's) is 155 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3827 cubic inches of down fill volume.
Feathered Friends Eos(Men's - Women's)	8/-13	No data	No data	No data	No data			No	No	Yes	Down	900	105	3,333	N/A	N/A	Pertex Quantum	All Round	Regular	306 g / 10.8 oz	?	No						bestdownjackets	Fill weight of Feathered Friends Eos(Men's - Women's) is 105 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 3333 cubic inches of down fill volume.
Feathered Friends Khumbu (Men's)	-17/-27	No data	No data	No data	No data			No	No	Yes	Down	900	378	12,000	Primaloft Gold	200 g	Pretex Shield XT	All Round	Regular	960 g / 2 lb 2 oz	?	No						bestdownjackets	Fill weight of Feathered Friends Khumbu (Men's) is 378 grams. Its fill power is 900 cubic inches per ounce, which equals to a total of 12000 cubic inches of down fill volume. It's also reinforced with 200 g of Primaloft Gold.
Mountain Equipment Exo (Men's)	-10/-23	No data	No data	No data	No data			No	Yes	Yes	Down	800	265	7,478	N/A	N/A	Nylon	All Round	Regular	770 g / 1 lb 11.2 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Mountain Equipment Exo (Men's) is 265 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 7478 cubic inches of down fill volume.
Mountain Equipment K7 (Men's)	-13/-25	No data	No data	No data	No data			No	Yes	Yes	Down	800	300	8,466	N/A	N/A	30D Drilite	All Round	Regular	820 g / 1 lb 13 oz	76 cm / 30 in	No						bestdownjackets	Fill weight of Mountain Equipment K7 (Men's) is 300 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8466 cubic inches of down fill volume.
Mountain Hardwear GW/2 (Men's - Women's)	28/-2	No data	No data	No data	No data			No	No	Yes	Down	800	85	2,399	N/A	N/A	10D Ripstop Nylon	All Round	Trim	250 g / 8.8 oz	70 cm / 27.5 in	No						bestdownjackets	Fill weight of Mountain Hardwear GW/2 (Men's - Women's) is 85 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 2399 cubic inches of down fill volume.
Outdoor Research Sup. Alp. (Men's - Women's)	3/-16	No data	No data	No data	No data			No	Yes	No	Down	800	182	5,136	N/A	N/A	30D Pertex Quantum Pro	All Round	Regular	825 g / 1 lb 13.1 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Outdoor Research Sup. Alp. (Men's - Women's) is 182 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5136 cubic inches of down fill volume.
Patagonia AlpLight (Men's - Women's)	36/2	No data	No data	No data	No data			No	No	Yes	Down	800	100	2,822	N/A	N/A	0.8 oz 10D polyester	All Round	Slim	270 g / 9.5 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia AlpLight (Men's - Women's) is 100 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 2822 cubic inches of down fill volume.
Patagonia AlpLoft (Men's)	-10/-23	No data	No data	No data	No data			No	Yes	Yes	Down	800	295	8,325	N/A	N/A	Pertex Quantom	All Round	Regular	680 g / 1 lb 8 oz	81 cm / 31.8 in	No						bestdownjackets	Fill weight of Patagonia AlpLoft (Men's) is 295 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8325 cubic inches of down fill volume.
Patagonia DAS (Men's - Women's)	10/-12	1/10	9/10	3/10	6/10		Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	PrimaLoft Gold Insulation Eco	133 + 40 g	Pertex Quantum Pro	All Round	Regular	555 g / 1 lb 3.6 oz	84 cm / 33 in	No			bestsyntheticjackets	2x dump	1x chest		Patagonia DAS (Men's - Women's) is equipped with 133 + 40 g of PrimaLoft Gold Insulation Eco.
Patagonia DAS Light(Men's)	34/1	2/10	8/10	2/10	9/10		Review	No	Yes	Yes	Synthetic	N/A	N/A	N/A	PlumaFill	65 g	10D Pertex Quantum Pro	All Round	Regular	320 g / 11.3 oz	77 cm / 30.5 in	No			bestsyntheticjackets	-	1x chest		Patagonia DAS Light(Men's) is equipped with 65 g of PlumaFill.
Patagonia Down Sweater (Men's - Women's)	23/-5	No data	4/10	6/10	7/10		Review	No	No	Yes	Down	800	150	4,233	N/A	N/A	1.4 oz 20x30D polyester	All Round	Regular	428 g / 15.1 oz	67 cm / 26.25 in	No						bestdownjackets	Fill weight of Patagonia Down Sweater (Men's - Women's) is 150 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 4233 cubic inches of down fill volume.
Patagonia Downdrift (Men's - Women's)	18/-8	No data	No data	No data	No data			No	No	No	Down	600	279	5,905	N/A	N/A	4.2 oz polyester	Around Town	Regular	1.014 kg / 2 lb 3.8 oz	?	No						bestdownjackets	Fill weight of Patagonia Downdrift (Men's - Women's) is 279 grams. Its fill power is 600 cubic inches per ounce, which equals to a total of 5905 cubic inches of down fill volume.
Patagonia Fitz Roy (Men's - Women's)	14/-10	No data	No data	No data	No data			No	No	Yes	Down	800	128	3,612	N/A	N/A	20D Nylon	All Round	Regular	632 g / 1lb 6.3 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia Fitz Roy (Men's - Women's) is 128 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 3612 cubic inches of down fill volume.
Patagonia Isthmus (Men's)	36/2	No data	No data	No data	No data			No	No	No	Parka	N/A	N/A	N/A	ThermoGreen	60 g	4.2 oz polyester	Around Town	Regular	895 g / 1 lb 15.6 oz	70 cm / 27.5 in	No							Patagonia Isthmus (Men's) is equipped with 60 g of ThermoGreen.
Patagonia Jackson Glacier (Men's - Women's)	12/-11	No data	No data	No data	No data		Review	No	Yes	No	Down	700	141	3,482	N/A	N/A	3.6 oz 50D polyester	Around Town	Regular	880 g / 1 lb 15 oz	79 cm / 31 in	No						bestdownjackets	Fill weight of Patagonia Jackson Glacier (Men's - Women's) is 141 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3482 cubic inches of down fill volume.
Patagonia Jackson Glacier Parks ( Women's)	7/-14	No data	No data	No data	No data			No	No	No	Parka	700	218	5,383	N/A	N/A	50D Polyester	Around Town	Regular	1.142 kg / 2 lb 8.3 oz	?	No							Fill weight of Patagonia Jackson Glacier Parks ( Women's) is 218 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 5383 cubic inches of down fill volume.
Patagonia Micro Puff (Men's - Women's)	37/3	5/10	6/10	5/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	PlumaFill	65 g	Pertex Quantum	All Round	Regular	298 g / 10.5 oz	75 cm / 29.5 in	No			bestsyntheticjackets	2x dump	-		Patagonia Micro Puff (Men's - Women's) is equipped with 65 g of PlumaFill.
Patagonia Nano Air (Men's - Women's)	39/4	7/10	5/10	5/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	FullRange	60 g	33D nylon ripstop	All Round	Trim	401 g / 14.14 oz	?	No			bestsyntheticjackets	-	2x chest		Patagonia Nano Air (Men's - Women's) is equipped with 60 g of FullRange.
Patagonia Nano Air Light Hybrid (Men's - Women's)	50/10	No data	No data	No data	No data			No	No	No	Synthetic	N/A	N/A	N/A	FullRange	40 g	20D nylon ripstop	All Round	Trim	335 g / 11.8 oz	?	No							Patagonia Nano Air Light Hybrid (Men's - Women's) is equipped with 40 g of FullRange.
Patagonia Nano Puff (Men's - Women's)	41/5	4/10	6/10	6/10	8/10		Review	No	No	Yes	Synthetic	N/A	N/A	N/A	PrimaLoft Gold Insulation Eco	60 g	22D Polyester	All Round	Regular	363 g / 12.8 oz	71.5 cm / 28 in	No			bestsyntheticjackets	1x chest	-		Patagonia Nano Puff (Men's - Women's) is equipped with 60 g of PrimaLoft Gold Insulation Eco.
Patagonia Silent Down (Men's - Women's)	26/-3	No data	No data	No data	No data		Review	No	No	No	Down	700	109	2,691	N/A	N/A	2.2 oz polyester	Around Town	Regular	585 g / 1 lb 4.7 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Patagonia Silent Down (Men's - Women's) is 109 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2691 cubic inches of down fill volume.
Patagonia Stormshadow (Men's)	0/-18	No data	No data	No data	No data			No	No	No	Parka	700	259	6,395	N/A	N/A	75D Polyester	Around Town	Regular	1.182 kg / 2 lb 9.7 oz	?	No							Fill weight of Patagonia Stormshadow (Men's) is 259 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 6395 cubic inches of down fill volume.
Patagonia Tres 3-in-1Patagonia Tres 3-in-1 (Men's - Women's)	8/-13	No data	No data	No data	No data		Review	No	No	No	Parka	700	118	2,914	N/A	N/A	5.5 oz polyester	Around Town	Regular	1.307 kg / 2 lb 14.1 oz	85 cm / 33.5 in	No							Fill weight of Patagonia Tres 3-in-1Patagonia Tres 3-in-1 (Men's - Women's) is 118 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 2914 cubic inches of down fill volume.
Patagonia Vosque 3-in-1 (Women's)	10/-12	No data	No data	No data	No data		Review	No	No	No	Parka	N/A	N/A	N/A	ThermoLite	100 g	65% nylon, 35% polyester	Around Town	Regular	1.360 kg / 3 lb	90 cm / 35.5 in	No							Patagonia Vosque 3-in-1 (Women's) is equipped with 100 g of ThermoLite.
Rab Electron Pro (Men's - Women's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	800	180	5,079	N/A	N/A	20D Pertex Quantum Pro	All Round	Regular	525 g / 1 lb 2.5 oz	74 cm / 29 in	No						bestdownjackets	Fill weight of Rab Electron Pro (Men's - Women's) is 180 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5079 cubic inches of down fill volume.
Rab Infinity Alpine (Men's)	5/-15	No data	No data	No data	No data			No	Yes	Yes	Down	800	175	4,938	N/A	N/A	30D & 13D Gore-Tex Infinium	All Round	Regular	551 g / 1 lb 3.4 oz	76.5 cm / 30.1 in	No						bestdownjackets	Fill weight of Rab Infinity Alpine (Men's) is 175 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 4938 cubic inches of down fill volume.
Rab Infinity Microlight (Men's - Women's)	19/-7	No data	No data	No data	No data			No	No	Yes	Down	700	146	3,605	N/A	N/A	13D Gore-Tex Infinium	All Round	Regular	452 g / 15.9 oz	74 cm / 29.1 in	No						bestdownjackets	Fill weight of Rab Infinity Microlight (Men's - Women's) is 146 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3605 cubic inches of down fill volume.
Rab Microlight Alpine (Men's - Women's)	7/-14	No data	No data	No data	No data			No	No	Yes	Down	700	153	3,778	N/A	N/A	30D Pertex Quantum	All Round	Regular	466 g / 1 lb 0.5 oz	72 cm / 28.5 in	No						bestdownjackets	Fill weight of Rab Microlight Alpine (Men's - Women's) is 153 grams. Its fill power is 700 cubic inches per ounce, which equals to a total of 3778 cubic inches of down fill volume.
Rab Neutrino Pro (Men's - Women's)	-2/-19	No data	No data	No data	No data			No	Yes	Yes	Down	800	212	5,982	N/A	N/A	20D Pertex Quantum Pro	All Round	Regular	585 g / 1 lb 8.6 oz	77 cm / 30.3 in	No						bestdownjackets	Fill weight of Rab Neutrino Pro (Men's - Women's) is 212 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 5982 cubic inches of down fill volume.
Rab Positron Pro (Men's)	-13/-25	No data	No data	No data	No data			No	Yes	Yes	Down	800	300	8,466	N/A	N/A	40D Pertex Quantum Pro	All Round	Regular	740 g / 1 lb 10 oz	85 cm / 33.5 in	No						bestdownjackets	Fill weight of Rab Positron Pro (Men's) is 300 grams. Its fill power is 800 cubic inches per ounce, which equals to a total of 8466 cubic inches of down fill volume.
REI Magma 850 Hoodie 2.0 (Men's - Women's)	14/-10	No data	No data	No data	No data			No	No	Yes	Down	850	120	3,598	N/A	N/A	Pertex mini ripstop nylon	All Round	Regular	340 g / 13.75 oz	74 cm / 29.25 in	No						bestdownjackets	Fill weight of REI Magma 850 Hoodie 2.0 (Men's - Women's) is 120 grams. Its fill power is 850 cubic inches per ounce, which equals to a total of 3598 cubic inches of down fill volume.

Performance data axis of synthetic jackets (this table) and shell jackets (table below) are different. Don't compare them.

Best synthetic insulated jackets: https://outdoorcrunch.com/synthetic-insulated-jackets/

Performance ratings of Arc'teryx shells

Name	Activity	Temp (F/C)	Breathability	Weather Res.	Durability	Packability	Bottom line	Review	Pit zips?	Two way zipper?	Stuffs into itself?	Face Fabric	Fit	Weight	Length	Discontinued?
Alpha (aka AR) (Men's - Women's)	Climbing	N/A	8/10	9/10	8/10	4/10	Go-to climbing harshell.	Review	Yes	No	No	N40d & N80d Most Rugged 3L Gore-Tex Pro	Regular	430 g / 15.2 oz	79.5 cm / 31.25 in	No
Alpha SV (Men's - Women's)	Climbing	N/A	8/10	10/10	10/10	3/10	Strongest climbing hardshell.	Review	Yes	No	No	N100d Most Rugged 3L Gore-Tex Pro	Regular	510 g / 1 lb 2 oz	78 cm / 30.75 in	No
Beta (Men's - Women's)	All Round	N/A	6/10	7/10	7/10	8/10	Streamlined all-doer shell.	Review	No	No	No	N30p-X 3L Gore-Tex	Trim	300 g / 10.6 oz	76 cm / 30 in	No
Beta AR (Men's - Women's)	All Round	N/A	8/10	9/10	9/10	4/10	Go-to all-round harshell.	Review	Yes	No	No	N40d & N80d Most Rugged 3L Gore-Tex Pro	Regular	460 g / 1 lb	76 cm / 30 in	No
Beta AR StormHood (Men's - Women's)	All Round	N/A	8/10	9/10	9/10	4/10		Review	Yes	No	No	N40d & N80d Most Rugged 3L Gore-Tex Pro	Regular	460 g / 1 lb	76 cm / 30 in	No
Beta Coat (Women's)	All Round	N/A	6/10	5/10	No data	5/10			No	Yes	No	3L Gore-Tex	Regular	320 g / 11.3 oz	88 cm / 34.5 in	No
Beta Down Insulated (Men's)	All Round	0/-18	9/10	7/10	8/10	No data			Yes	Yes	No	2L 40D Gore-Tex	Regular	760 g / 1 lb 10.8 oz	79 cm / 31 in	No
Beta Insulated (Men's - Women's)	All Round	21/-6	9/10	7/10	8/10	No data	Go-to hybrid jacket.	Review	Yes	Yes	No	N40d 2L Gore-Tex	Regular	680 g / 1 lb 8 oz	78.5 cm / 31 in	No
Beta Insulated Coat (Women's)	All Round	16/-9	7/10	No data	No data	No data			No	Yes	No	N40d 2L Gore-Tex	Regular	600 g / 1 lb 5.2 oz	86 cm / 34 in	No
Beta Lightweight (Men's - Women's)	All Round	N/A	8/10	7/10	7/10	6/10		Review	Yes	No	No	N40p 3L Gore-Tex	Fitted	380 g / 13.4 oz	75 cm / 29.5 in	No
Beta LT (Men's - Women's)	All Round	N/A	7/10	7/10	8/10	6/10		Review	Yes	No	No	N40d 3L Gore-Tex	Fitted	395 g / 13.9 oz	76 cm / 30 in	No
Gamma (aka LT) (Men's - Women's)	All Round	N/A	7/10	3/10	7/10	3/10	Go-to softshell.	Review	No	No	No	Wee Burly Double Weave	Regular	545 g / 1 lb 3.2 oz	76 cm / 30 in	No
Gamma MX (Men's)	All Round	N/A	6/10	4/10	8/10	3/10	Strongest softshell.	Review	No	No	No	Fortius 2.0	Regular	555 g / 1 lb 3.6 oz	74 cm / 29.1 in	No
Norvan Shell (Men's)	Running	N/A	No data	No data	No data	No data			No	No	No	13D 3L Gore-Tex	Trim	190 g / 6.7 oz	73 cm / 28.75 in	No
Rush (Women's)	Skiing	N/A	8/10	9/10	9/10	3/10	Go-to ski jacket.	Review	Yes	No	No	N80p-X & N100p-X 3L Most Rugged Gore-Tex Pro	Regular	590 g / 1 lb 4.8 oz	79.5 cm / 31.25 in	No
Rush Insulated (Women's)	Skiing	16/-9	3/10	5/10	5/10	9/10		Review	No	No	Yes	Hadron 2L Gore-Tex Infinium	Regular	515 g / 1 lb 2.2 oz	79 cm / 31 in	Yes
Sabre (Men's)	Skiing	N/A	8/10	8/10	7/10	2/10		Review	Yes	No	No	N80p-X 3L Gore-Tex	Regular	705 g / 1 lb 8.9 oz	79 cm / 31 in	No
Sentinel (Women's)	Skiing	N/A	8/10	7/10	7/10	2/10	Go-to ski jacket.	Review	Yes	No	No	N70p 3L Gore-Tex	Regular	640 g / 1 lb 6.6 oz	73.7 cm / 29 in	No
Sentinel Insulated (Women's)	Skiing	21/-6	8/10	No data	No data	No data		Review	Yes	No	No	N80p 2L Gore-Tex	Regular	600 g / 1 lb 5.2 oz	79.8 cm / 31.5 in	No
Sentinel Relaxed (Women's)	Skiing	N/A	No data	No data	No data	No data			Yes	No	No	N80p 3L Gore-Tex	Regular	655 g / 1 lb 7.1 oz	?	No
Sidewinder (Women's)	Skiing	N/A	8/10	8/10	7/10	2/10			Yes	No	No	N80p 3L Gore-Tex	Regular	570 g / 1 lb 4.1 oz	?	No
Solano (Men's - Women's)	Around Town	N/A	No data	No data	No data	No data		Review	No	No	No	Gore-Tex Infinium	Relaxed	355 g / 12.5 oz	72 cm / 28.3 in	No
Squamish (Men's - Women's)	Running	N/A	5/10	4/10	7/10	9/10	Go-to running jacket.	Review	No	No	Yes	30D Tyono	Trim	140 g / 4.9 oz	77.5 cm / 30.5 in	No
Theriss Down (Women's)	Skiing	No data	7/10	6/10	7/10	2/10		Review	Yes	No	No	N80p 2L Gore-Tex	Regular	709 g / 1 lb 9 oz	63 cm / 24.8 in	No
Alpha FL (Men's - Women's)	Climbing	N/A	7/10	No data	No data	10/10			No	No	Yes	Hadron 3L Gore-Tex	Trim	209 g / 7.4 oz	76.5 cm / 30 in	Yes
Alpha IS (Men's)	Climbing	23/-5	7/10	5/10	No data	8/10			No	Yes	Yes	N40p-X 2L Gore-Tex	Regular	610 g / 1 lb 5.5 oz	78 cm / 30.75 in	Yes
Alpha SL (Men's - Women's)	Climbing	N/A	5/10	7/10	No data	9/10			No	No	Yes	N40p 3L Gore-Tex	Trim	326 g / 11.5 oz	77.5 cm / 30.5 in	Yes
Beta SV (Men's - Women's)	All Round	N/A	8/10	10/10	10/10	3/10	Strongest all-round harshell.	Review	Yes	No	No	N80p-X Most Rugged 3L Gore-Tex Pro	Regular	495 g / 1 lb 1.5 oz	79 cm / 31 in	Yes
Gamma SL (aka lightweight) (Men's - Women's)	All Round	N/A	7/10	2/10	6/10	5/10		Review	No	No	No	Fortius 1.0	Trim	310 g / 10.9 oz	74 cm / 29.1 in	Yes
Incendia (Women's)	Skiing	N/A	8/10	9/10	9/10	3/10		Review	Yes	No	No	NP100d 3L Gore-Tex	Trim	610 g / 1 lb 5.5 oz	79 cm / 31 in	Yes
Incendo (Men's)	Running	N/A	7/10	4/10	5/10	10/10		Review	No	No	Yes	Lumin	Trim	125 g / 4.4 oz	?	Yes
Incendo Airshell (Men's	Running	N/A	No data	No data	No data	No data			No	No	Yes	?	Trim	105 g / 3.7 oz	?	Yes
Incendo SL (Men's)	Running	N/A	7/10	4/10	4/10	10/10		Review	No	No	Yes	Permair 20 & Canim	Trim	80 g / 2.8 oz	73 cm / 28.75 in	Yes
Macai (Men's)	Skiing	5/-15	7/10	7/10	6/10	1/10		Review	Yes	No	No	N40p-X 3L Gore-Tex	Regular	990 g / 2 lb 2.9 oz	75 cm / 29.5 in	Yes
Macai Lightweight (aka LT) (Men's)	Skiing	8/-13	7/10	7/10	6/10	2/10		Review	Yes	No	No	N40p-X 3L Gore-Tex	Regular	855 g / 1 lb 14.2 oz	?	Yes
Macai Shell (Men's)	Skiing	N/A	No data	No data	No data	No data		Review	Yes	No	No	N80p-X 3L Gore-Tex	Regular	775 g / 1 lb 11.3 oz	?	Yes
Micon (Men's)	Skiing	N/A	No data	No data	No data	No data			Yes	No	No	N80p 3L Gore-Tex	Regular	685 g / 1 lb 8.2 oz	83 cm / 32.5 in	Yes
Micon Heather	Skiing	N/A	No data	No data	No data	No data			Yes	No	No	NP100-d 3L Gore-Tex	Regular	685 g / 1 lb 8.2 oz	83 cm / 32.5 in	Yes
Nodin (Men's - Women's)	Running	N/A	8/10	5/10	5/10	10/10			No	No	Yes	20D Tyono	Trim	130 g / 4.6 oz	75 cm / 29.5 in	Yes
Norvan LT (Men's - Women's)	Running	N/A	5/10	5/10	8/10	6/10			No	No	No	N13p 3L Gore-Tex	Trim	190 g / 6.7 oz	?	Yes
Norvan SL (Men's - Women's)	Running	N/A	7/10	6/10	8/10	8/10		Review	No	No	Yes	Gore-Tex Infinium	Trim	120 g / 4.2 oz	77 cm / 30.4 in	Yes
Norvan SL Ins. (Women's)	Running	39/4	No data	No data	No data	No data			No	No	Yes	Gore-Tex ShakeDry	Trim	270 g / 9.5 oz	71.5 cm / 28.1 in	Yes
Norvan Windshell (Men's	Running	N/A	No data	No data	No data	No data			No	No	Yes	Permeair 20	Trim	90 g / 3.2 oz	73 cm / 28.75 in	Yes
Procline (Men's)	Skiing	N/A	No data	No data	No data	No data			Yes	No	No	N70p Gore-Tex Infinium	Trim	720 g / 1 lb 9.4 oz	76 cm / 30 in	Yes
Ravenna (Women's)	Skiing	N/A	8/10	7/10	8/10	3/10		Review	Yes	No	No	N70s-4 3L Gore-Tex	Trim	725 g / 1 lb 9.6 oz	69.5 cm / 27.4 in	Yes
Ravenna LT (Women's)	Skiing	N/A	6/10	6/10	6/10	5/10		Review	Yes	No	No	N70p 3L Gore-Tex	Trim	540 g / 1 lb 3 oz	69 cm / 27.2 in	Yes
Sabre AR (Men's)	Skiing	N/A	7/10	8/10	7/10	7/10		Review	Yes	No	No	N70p 3L Gore-Tex	Regular	700 g / 1 lb 8.7 oz	79 cm / 31 in	Yes
Sabre Insulated (See related products)	Skiing	No data	7/10	No data	6/10	No data		Review	Yes	No	No	N80p 2L Gore-Tex	Regular	815 g / 1 lb 12.7 oz	76 cm / 30 in	Yes
Sabre LT (Men's)	Skiing	N/A	7/10	8/10	7/10	8/10		Review	Yes	No	No	N80p 3L Gore-Tex	Regular	660 g / 1 lb 7.3 oz	83 cm / 32.5 in	Yes
Sabre SV (Men's)	Skiing	N/A	10/10	10/10	10/10	1/10	Strongest ski jacket.	Review	Yes	Yes	No	N100d Most Rugged 3L Gore-Tex Pro	Regular	595 g / 1 lb 5 oz	85 cm / 33.5 in	No
Sentinel AR (Women's)	Skiing	N/A	7/10	8/10	7/10	7/10		Review	Yes	No	No	N70p 3L Gore-Tex	Regular	590 g / 1 lb 4.8 oz	72.5 cm / 28.5 in	Yes
Sentinel LT (Women's)	Skiing	N/A	7/10	8/10	7/10	8/10		Review	Yes	No	No	N80p 3L Gore-Tex	Regular	565 g / 1 lb 3.9 oz	73.5 cm / 29 in	Yes
Shashka Stretch (Women's)	Skiing	N/A	No data	No data	No data	No data			Yes	No	No	N70p Gore-Tex Infinium	Trim	670 g / 1 lb 7.6 oz	71 cm / 28 in	Yes
Trino SL (Men's)	Running	N/A	8/10	5/10	7/10	6/10		Review	No	No	No	Gore-Tex Infinium	Trim	340 g / 12 oz	74 cm / 29.1 in	Yes
Trino SL Anorak (Women's)	Running	N/A	8/10	7/10	8/10	7/10		Review	No	No	No	Gore-Tex Infinium	Trim	290 g / 10.2 oz	65 cm / 25.5 in	Yes
Venda Anorak (Women's)	Around Town	N/A	No data	No data	No data	No data			No	No	No	Gore-Tex	Relaxed	255 g / 9 oz	75.5 cm / 29.7 in	Yes
Zeta AR (Men's)	Hiking	N/A	7/10	8/10	7/10	4/10			Yes	No	No	3L Gore-Tex	Regular	425 g / 15 oz	80 cm / 31.5 in	Yes
Zeta FL (Men's - Women's)	Hiking	N/A	4/10	6/10	4/10	6/10			No	No	No	N20r 2L Gore-Tex	Trim	221 g / 7.8 oz	76 cm / 30 in	Yes
Zeta LT (Men's - Women's)	Hiking	N/A	5/10	7/10	8/10	5/10			No	No	No	N40P-X 3L Gore-Tex	Trim	335 g / 11.8 oz	78 cm / 30.75 in	Yes
Zeta SL (Men's - Women's)	Hiking	N/A	3/10	5/10	4/10	5/10		Review	No	No	No	2L Gore-Tex	Trim	310 g / 10.9 oz	77.8 cm / 30.6 in	Yes

Performance data axis of synthetic jackets (table above) and shell jackets (this table) are different. Don't compare them.

Patagonia and Arc'teryx are like up to 70% off at REI rn...
- https://www.rei.com/h/deals

Breathability

Going from top to bottom (Atom SL, LT and AR respectively), the warmth increases and the breathability decreases.

Although Atom SL is the most breathable unit in the Atom line, Proton FL still breathes more.

Actually, as I explained before, this is also the case between Proton and Atom as well.

Water, wind and abrasion resistances

While neither are comparable to outer layers (shell or belay jackets) at all, they'll fill the bill for spring and summer activities.

They're both DWR coated.

What is DWR by the way?

DWR is a coating.

It's basically sprayed on to the surface of these jackets as a finish.

It stands for Durable Water Repellent - which means that water will be repelled under wet conditions instead of soaking into the fabric.

DWR also decreases dry time.

It's a good thing these jackets are coated in DWR.

But pay attention to the fact that DWR is a coating - meaning that it will wear off over time.

Which is why you might want to invest in a DWR spray such as this one at arcteryx.com for after treatment.

As you see, there's a strong correlation between FP x FW and temperature ratings, but not more than, say, 80%. I explained why this happens here in this post of mine.