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):
Name | Activity | Temp (F/C) | Breathability | Weather Res. | Durability | Bottom line | Review | Pit zips? | Two way zipper? | Stuffs into itself? | Face Fabric | Fit | Weight | Length | ||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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 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 | ||
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 |
Andessa (Women's) | Skiing | 8/-13 | 10/10 | No data | No data | 1/10 | Yes | No | No | N40d 3L Gore-Tex | Trim | 869 g / 1 lb 14.7 oz | 67 cm / 26.4 in | Yes | ||
Andessa Shell (Women's) | Skiing | N/A | 5/10 | No data | No data | 3/10 | No | No | No | N70p 3L Gore-Tex | Trim | 560 g / 1 lb 3.8 oz | ? | Yes | ||
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 Long | All Round | N/A | 4/10 | 9/10 | No data | 3/10 | Review | No | No | No | N80p 3L Gore-Tex | Regular | 441 g / 15.6 oz | 85 cm / 33.5 in | Yes | |
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 | |
Beta LT Hadron | All Round | N/A | 7/10 | 6/10 | 4/10 | 5/10 | No | No | No | Hadron 3L Gore-Tex | Fitted | 255 g / 9 oz | 76 cm / 30 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 |
Cassiar (Men's) | Skiing | N/A | 8/10 | 7/10 | 8/10 | 3/10 | Review | Yes | No | No | N70p 3L Gore-Tex | Trim | 820 g / 1 lb 12.9 oz | 74.5 cm / 29.3 in | Yes | |
Cassiar LT (Men's) | Skiing | N/A | 6/10 | 6/10 | 6/10 | 5/10 | Review | Yes | No | No | N70p 3L Gore-Tex | Trim | 605 g / 1 lb 5.3 oz | 75 cm / 29.5 in | Yes | |
Cita (Women's) | Running | N/A | 7/10 | 4/10 | 5/10 | 10/10 | Review | No | No | Yes | Lumin | Trim | 120 g / 4.2 oz | 67.5 cm / 26.5 in | Yes | |
Cita SL (Women's) | Running | N/A | 7/10 | 4/10 | 4/10 | 10/10 | Review | Yes | No | Yes | Permeair 20 | Trim | 65 g / 2.3 oz | 61.5 cm / 24.2 in | Yes | |
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 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 | |
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 |
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 | |
Indencia IS | Skiing | No data | No data | No data | No data | No data | Yes | No | No | N80p 2L Gore-Tex | Regular | ? | 78 cm / 30.75 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 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 | ||
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 | |
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 (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 | No | |
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 | |
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 | Yes |
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 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 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 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 | |
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 | ||
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 | ||
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 | |
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...
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.
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.
Fit and size measurements
For a small size Atom SL:
- Chest width: 107 cm
- Shoulder length: 16.4 cm
- Waist width: 98.4 cm
- Front length: 67.3 cm
- Center back length: 71 cm
For a small size Proton FL:
- Chest width: 109 cm
- Shoulder length: 14.8 cm
- Waist width: 101.0 cm
- Front length: 75.7 cm
- Center back length: 75.7 cm
Both offer a trim cut.
Conclusion
I'd probably get the Proton FL. It's more versatile.
A helpful video review:
- Poll results: Giant Arc'teryx & Patagoina survey (Gore-Tex, pockets, hoods, fit, & more) [1000+ participated]
- Pics from outrageous discounts I ran into at Arc'teryx Parndorf Outlet
- I bought Gamma Lightweight (aka SL), Gamma (aka LT) and Gamma MX
- Patera Parka (one year update): Ain't worth the price...
- Alpha vs Beta: I bought all 4 Beta's and both Alpha's. Settling this for good
- Proton Hybrid: A "hidden" way to stuff it in itself!?
- Best Insulated Jackets: A hands-on Arc'teryx & Patagonia face-off
- 2024 Nano Air is in! Bought it immediately...
- I bought all 7 of Winter '24 Atom and Proton jackets
- Best Arc'teryx Ski Jackets: Rush is ideal, Sabre SV is overkill
- Arc’teryx colors: Most and least liked (poll results)
- Took my Nuclei SV to the Alps near Pfander, Austria
- Arc'teryx Alpha Parka Review: The most impressive jacket of all time
- Arc'teryx ReGEAR: OutdoorCrunch exclusive promo code!
- Beta Insulated Jacket is in: Pit zips AND two way zipper
- DropHood vs StormHood: Pros/cons and best uses
- 7 things all Arc'teryx newbies should know
Check out our other content on jackets:
Guide: Insulated & Shell Jackets
Start here:
Also see: