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

Update: Our in-depth comparison of the Arc'teryx Atom SL (Atom Lightweight) vs the Proton Lightweight (formerly Proton FL) can be found at https://outdoorcrunch.com/arcteryx-proton-vs-atom/.

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

Poll results: Best colorways of Atom Series

Upvote your favorites.

Atom LT Jacket Men's

Black

Kingfisher

Void

Canvas

Quick links:

https://arcteryx.com/shop/mens/atom-lt-jacket

https://outdoorcrunch.com/arcteryx-proton-lt-vs-atom-lt/

Atom LT Hoody Men's

Void

Canvas

Black

Solace

Heritage

Fika/Black Sapphire

Kingfisher

Quick links:

https://arcteryx.com/shop/mens/atom-lt-hoody

https://outdoorcrunch.com/nano-puff-vs-atom-lt/

Atom SL Hoody Men's

Serene

Black

Canvas

Jungle Maze

Sprint

Solitude

Quick links:

https://arcteryx.com/shop/mens/atom-sl-hoody

https://outdoorcrunch.com/arcteryx-atom-lt-vs-sl/

Atom Hoody Women's

Techno

Atmos

Sprint

Black

Orca

Solace

Fika/Spark

Black Sapphire

Expanse

Velvet Sand

Labyrinth

Quick links:

https://arcteryx.com/shop/womens/atom-hoody

Atom Lightweight Hoody Women's

Wicker/Sprint

Solitude

Groovie

Black

Bliss/Spark

Serene

Quick links:

https://arcteryx.com/shop/womens/atom-lightweight-hoody

Atom Jacket Women's

Black

Solace

Quick links:

https://arcteryx.com/shop/womens/atom-jacket

Atom Heavyweight Hoody Women's

Synth

Habitat

Moonlit

Black

Quick links:

https://arcteryx.com/shop/womens/atom-heavyweight-hoody

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)	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?
Arc'teryx Alpha Parka (Men's - Women's)	-18/-28	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
Arc'teryx Alpha Lightweight (Men's - Women's)	5/-15		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
Arc'teryx Atom (aka LT) ( Men's - Women's)	43/6	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
Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's)	18/-8	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
Arc'teryx Atom Lightweight (aka SL) (Men's - Women's)	52/11	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
Arc'teryx Beta Down Insulated (Men's)	0/-18		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
Arc'teryx Beta Insulated (Men's)	21/-6	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
Arc'teryx Beta Insulated Coat (Women's)	16/-9	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
Arc'teryx Cerium (aka LT) (Men's - Women's)	26/-3	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
Arc'teryx Cerium Hybrid (Women's)	44/7		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
Arc'teryx Coelle (Women's)	14/-10		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 Liatris (Women's)	5/-15		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
Arc'teryx Liatris Parka (Women's)	2/-17		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
Arc'teryx Nuclei (aka FL) ( Men's - Women's)	32/0	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
Arc'teryx Nuclei SV (Women's)	5/-15	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
Arc'teryx Patera (Women's)	21/-6	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
Arc'teryx Patera Long (Women's)	0/-18		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
Arc'teryx Proton Lightweight (aka FL) (Men's - Women's)	48/9	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
Arc'teryx Therme Parka (Men's)	5/-15	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
Arc'teryx Therme SV (Men's)	-11/-24	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
Arc'teryx Thorium ( Men's - Women's)	12/-11	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
Arc'teryx Thorium Parka (Women's)	-2/-19	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
Arc'teryx Thorium SV (Men's)	3/-16		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
Arc'teryx Thorium SV Parka (Men's)	0/-18		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
Black Diamond Access Down (Men's - Women's)	7/-14		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
Feathered Friends Eos(Men's - Women's)	8/-13		No	No	Yes	Down	900	105	3,333	N/A	N/A	Pertex Quantum	All Round	Regular	306 g / 10.8 oz	?	No
Feathered Friends Khumbu (Men's)	-17/-27		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
Mountain Equipment Exo (Men's)	-10/-23		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
Mountain Equipment K7 (Men's)	-13/-25		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
Mountain Hardwear GW/2 (Men's - Women's)	28/-2		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
Outdoor Research Sup. Alp. (Men's - Women's)	3/-16		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
Patagonia AlpLight (Men's - Women's)	36/2		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
Patagonia AlpLoft (Men's)	-10/-23		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
Patagonia DAS (Men's - Women's)	10/-12	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
Patagonia DAS Light(Men's)	34/1	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
Patagonia Down Sweater (Men's - Women's)	23/-5	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
Patagonia Downdrift (Men's - Women's)	18/-8		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
Patagonia Fitz Roy (Men's - Women's)	14/-10		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
Patagonia Isthmus (Men's)	36/2		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 Jackson Glacier (Men's - Women's)	12/-11	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
Patagonia Jackson Glacier Parks ( Women's)	7/-14		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
Patagonia Micro Puff (Men's - Women's)	41/5	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
Patagonia Nano Air (Men's - Women's)	41/5	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
Patagonia Nano Air Light Hybrid (Men's - Women's)	50/10		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 Puff (Men's - Women's)	37/3	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
Patagonia Silent Down (Men's - Women's)	26/-3	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
Patagonia Stormshadow (Men's)	0/-18		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
Patagonia Tres 3-in-1Patagonia Tres 3-in-1 (Men's - Women's)	8/-13	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
Patagonia Vosque 3-in-1 (Women's)	10/-12	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
Rab Electron Pro (Men's - Women's)	5/-15		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
Rab Infinity Alpine (Men's)	5/-15		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
Rab Infinity Microlight (Men's - Women's)	19/-7		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
Rab Microlight Alpine (Men's - Women's)	7/-14		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
Rab Neutrino Pro (Men's - Women's)	-2/-19		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
Rab Positron Pro (Men's)	-13/-25		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
REI Magma 850 Hoodie 2.0 (Men's - Women's)	14/-10		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

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)	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?
Arc'teryx Alpha Parka (Men's - Women's)	-18/-28	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
Arc'teryx Alpha Lightweight (Men's - Women's)	5/-15		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
Arc'teryx Atom (aka LT) ( Men's - Women's)	43/6	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
Arc'teryx Atom Heavyweight (aka AR) (Men's - Women's)	18/-8	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
Arc'teryx Atom Lightweight (aka SL) (Men's - Women's)	52/11	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
Arc'teryx Beta Down Insulated (Men's)	0/-18		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
Arc'teryx Beta Insulated (Men's)	21/-6	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
Arc'teryx Beta Insulated Coat (Women's)	16/-9	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
Arc'teryx Cerium (aka LT) (Men's - Women's)	26/-3	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
Arc'teryx Cerium Hybrid (Women's)	44/7		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
Arc'teryx Coelle (Women's)	14/-10		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 Liatris (Women's)	5/-15		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
Arc'teryx Liatris Parka (Women's)	2/-17		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
Arc'teryx Nuclei (aka FL) ( Men's - Women's)	32/0	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
Arc'teryx Nuclei SV (Women's)