Arc’teryx Atom SL Hoody

Price: $229
Weight: 9.4 oz. (men’s medium)
Insulation: 40g Coreloft Compact (core only)
What we like: Ultralight, versatile, and surprisingly great weather protection.
What we don’t: Limited warmth and only moderately breathable.
See the Men's Arc'teryx Atom SL  See the Women's Arc'teryx Atom SL


Within Arc’teryx’s popular Atom synthetic jacket series, the “SL” slots in as the lightest and most focused of the bunch. It isn’t very warm with insulation only in the torso and a minimalist, alpine-centric build, but over the past few years, this jacket has proven to be one of the most versatile pieces of gear I’ve tested. From mid-winter runs and backcountry tours to shoulder-season hikes, the Atom SL is an incredibly capable and well-rounded companion. Below we break down the Atom SL’s warmth, weather protection, breathability, weight and packability, durability, fit and sizing, and more. To see how it stacks up, see our articles on the best synthetic jackets and best midlayers.



Among synthetic jackets, the Arc’teryx Atom SL Hoody is a truly unique design. With thin, 40-gram Coreloft Compact insulation in the core and no fill elsewhere, it’s certainly not warm—I’m comfortable when inactive and hanging around camp in temperatures down to the low 50s Fahrenheit. However, paired with thoughtful touches like stretchy fleece side panels, a wind- and water-resistant shell, tall collar, and mesh lining on the upper arms, the Atom SL excels in a wide range of activities. It’s my favorite outer layer when running or skinning on snowy and frigid days (around 10 degrees and sometimes below). The shell cuts harsh wind, the non-insulated hood keeps me protected without overheating, and the snug fit maximizes warmth. Plus, I’ve found it to be a really nice balance for wearing on cool-weather shoulder-season hikes. In many ways, it functions like a lightly insulated windbreaker in these instances.Arc'teryx Atom SL Hoody synthetic jacket (hiking uphill)

As a midlayer, the Atom SL is equally versatile. Among hooded jackets, it’s one of the easiest to layer under a shell as the thin hood rolls or stuffs away behind my neck. I often wear it under my ski jacket for the descents while touring, and I also commonly use it for resort days towards the beginning and end of the season (or in milder weather when temperatures are hovering around freezing). Another layer of insulation will likely be necessary on especially cold days or extended backcountry trips, but the Atom SL strikes a nice middle ground for a fairly wide range of uses and conditions.Arc'teryx Atom SL Hoody synthetic jacket (layering under ski jacket)

Weather Protection

Unlike many current active insulation jackets, the Atom SL offers a fair amount of weather resistance. As I mentioned above, the shell fabric does a great job taking the sting out of head-on wind (the stretchy side panels allow quite a bit more air to come through). Combined with a durable water repellent (DWR) coating, the jacket effectively repels light rain and snow. To be clear, you’ll want to swap to a fully waterproof shell if the weather takes a serious turn, but I’ve been consistently impressed by how long I’m able to continue wearing the Atom SL, particularly in the snow. Additionally, since this is a synthetic piece, the jacket will continue to insulate when wet. And even when the shell fabric has given in and starts absorbing moisture, its thin build tends to dry out quickly (unless of course it’s stuffed away in a wet ski backpack). Arc'teryx Atom SL Hoody (Mount Baker viewpoint)

When it comes time to batten down the hatches, the Atom SL Hoody is well-equipped for the job. The hood is climbing helmet-compatible but cinches down nicely when wearing just a ballcap or beanie, and it even stays effectively in place when going without head protection at all. Rounding out the features, the collar sits tall on the face (it reaches my lower lip when zipped up), the hem cinches securely, and the jacket’s long arms and extended panels of fabric over the back of the hands increase coverage. All in all, considering its light and fairly minimalist build, the Atom SL is a surprisingly capable barrier against the elements.Arc'teryx Atom SL Hoody synthetic jacket (zipping up with hood)


While the Atom SL’s weather protection is impressive, it does come at the cost of breathability: the same shell fabric that repels wind unfortunately doesn’t do as good a job releasing hot air. And even with fleece-like side panels providing a place for wind to work its way through to regulate heat (they extend from the hem all the way under the arms to the wrists), the jacket runs fairly warm. The mesh lining around the arms is effective for pulling moisture away, but the less air-permeable shell still keeps it from being a standout ventilator. In the end, despite the minimal insulation, I rarely opt for the Atom SL for touring in moderate temperatures (20s Fahrenheit), especially if the sun is out. If breathability is a priority for activities like climbing or cold-weather running and you’re willing to give up some protection, an option like Arc’teryx’s own Proton FL makes more sense (although that jacket is even less warm than the Atom).Arc'teryx Atom SL Hoody synthetic jacket (fleece side panel)

Weight and Packability

The “SL” in the Atom’s name is short for superlight, and my men’s medium hoody backs that up with a 9.4-ounce weight on our scale (it’s listed at 9.2 oz.). This puts it well under the rest of the Atom lineup: the LT (“lightweight”) is 14.6 ounces while the AR (“all round”) clocks in at 16 ounces, although both options are significantly warmer with insulation throughout the entire build. The aforementioned Proton FL comes at 11.4 ounces, and Arc’teryx’s recently updated, climbing-specific Nuclei FL is also heavier at 11.5 ounces. Outside of Arc’teryx’s lineup, Outdoor Research’s Refuge Hybrid features a similar insulation design but comes in at 12.3 ounces. All in all, you’ll be hard-pressed to find comparable performance for less weight.

As expected, the Atom SL is quite packable too, although we’re disappointed Arc’teryx doesn’t include a stuff sack or dedicated pocket (which would be a logical fit given its weight and intended uses). That said, you can roll the jacket up into its hood and secure it with the cinch. Arc’teryx claims the jacket compresses to the size of a large grapefruit, which we mostly agree with, although it’s certainly on the bigger end of that spectrum.Arc'teryx Atom SL Hoody synthetic jacket (packed size)

Comfort and Mobility

Like its warmer siblings, the Arc’teryx Atom SL Hoody scores high marks in comfort. The interior lining is a mix of knit polyester along the sides and underarms, mesh in the upper half of the sleeves, and a thin synthetic around the core—all of which are soft and surprisingly cozy. Additionally, with the long sections of stretchy polyester along the sides and a trim fit, the jacket moves exceptionally well. This mobility makes it a nice match for a wide range of activities, from backcountry skiing to climbing to wearing every day in the shoulder seasons (provided the taller hand pockets aren’t a problem). It’s even a viable option for biking in the right temperatures, as the longer sleeves and extended back length offer great coverage.Arc'teryx Atom SL Hoody synthetic jacket (packing pack while snowshowing)

Features: Hood, Hem, Cuffs, and Pockets

Given its focus on shaving weight, the Atom SL has a fairly pared-down feature set. Starting with the StormHood, it’s sized to fit over a climbing helmet but is easily adjustable with a rear cinch that tightens both around the sides and top of the forehead. I’ve worn the hood in high winds while backpacking in Patagonia—strong enough that we had to lie down to keep from getting blown over—and it stayed securely in place. Further, the hem cinches behind the right hip, and pulling the drawcord secures the jacket around the back. This has proven to be an effective solution: the simple design keeps weight down, still seals solidly in place, and doesn’t pull the jacket to one side when tightened. The cuffs are equally well-thought-out: there’s soft and stretchy knit polyester along the bottom half, while the back of the hand has a longer length for added coverage. You don’t get a perfect seal, but the length and good all-around mobility mean they stay nicely in place even when reaching overhead.Arc'teryx Atom SL Hoody synthetic jacket (tightening rear hood adjustment)

In terms of storage, Arc’teryx stuck to the basics with two zippered hand pockets. These are set higher on the body, so you can easily access them when wearing a pack or climbing harness. The taller height does mean your hands don’t rest as naturally in them, which is a downside for daily use. However, the interiors are quite generous and can easily accommodate my gloved hands. And given the jacket’s performance intentions and the fact that there are no other storage options, this feels like a very reasonable compromise. Arc'teryx Atom SL Hoody synthetic jacket (hipbelt compatible pockets)

Build Quality and Durability

Ultralight products aren’t known for their durability, but Arc’teryx has toed a nice line between weight savings and toughness with the Atom SL. The jacket uses a 20-denier (D) shell fabric, which is undoubtedly light but significantly more durable than many UL models (one example is Patagonia’s ultra-thin 10D Micro Puff, which we found to be considerably more tear-prone). After more than three years of use, I can confidently say I’ve put the Atom SL through the wringer, and it’s still in fantastic shape. The shell has no tears, the interior still looks and feels great, and I’ve had no hiccups with the performance of the zippers or cinch cords. Even the stretchy fabrics along the side panels haven’t loosened or lost their shape. The only sign of wear is pilling at the interior of these panels, but the exterior still looks nearly like new. We set a high bar for Arc’teryx products, and the Atom SL has well exceeded our expectations.Arc'teryx Atom SL Hoody synthetic jacket (face fabric and logo)

Fit and Sizing

The Atom SL was one of the first Arc’teryx items I tested, and I immediately came to appreciate its excellent fit. The medium size has a trim cut that’s perfect for my build (for reference, I’m 5’9” and 155 lbs.). Combined with the excellent comfort from the stretchy fabrics, it’s been flawless for active and everyday use. I’ve worn the Atom SL over a range of baselayers (from ultralight to heavyweight) and never had an issue with mobility, and its low-profile design means it easily slides under a shell. Finally, as I touched on above, the jacket has a slightly longer cut at the back (29.1 in.) and fairly long arms, which are great for applications like climbing or cycling. That said, the length is still entirely workable for other activities or when wearing the jacket as a midlayer.Arc'teryx Atom SL Hoody synthetic jacket (hands in pockets)

Other Versions of the Arc’teryx Atom SL

We put the men’s Atom SL Hoody through its paces for this review, and Arc’teryx also makes the jacket in a women’s version. The women’s Atom SL Hoody costs the same at $229 and sports an identical build and feature set, but it’s lighter at 8.3 ounces and is available in different colorways (five at the time of publishing, including a bright magenta and orange). To round out the superlight offerings, Arc’teryx makes the Atom SL in a vest version. The men’s vest weighs just 5.6 ounces, costs $149, and is very similar in overall design to the hoody reviewed here.Arc'teryx Atom SL Hoody (unzipping tent in morning)

What We Like

  • Incredibly versatile: the Atom SL functions well as an outer layer for cold-weather running and backcountry skiing, but also works as a midlayer for resort use and other less aerobic activities.
  • Surprisingly solid weather protection for an active insulation piece.
  • One of the lightest synthetic jackets on the market at 9.2 ounces.
  • Despite the relatively thin 20-denier shell, the Atom SL is hardwearing and has held up impressively well—I have no tears in my jacket after three years of use.

What We Don’t

  • With 40-gram insulation only in the core, the Atom SL offers very limited warmth and isn’t a great match for true winter temperatures.
  • Breathability falls well short of other active insulation designs.
  • No stuff sack or dedicated stuff pocket.
  • Hand pockets are set a bit high for comfortably resting your hands, which is a downside for daily use.

Arc'teryx Atom SL Hoody synthetic jacket (hem adjustment)

Comparison Table

Jacket Price Weight Insulation Fabric Packable
Arc'teryx Atom SL Hoody $229 9.2 oz. Coreloft Compact (40g) 20D No
Arc'teryx Proton FL Hoody $259 11.4 oz. Octa Loft 20D No
Arc'teryx Nuclei FL $299 11.5 oz. Coreloft Continuous (65g) 10D Yes
Outdoor Research Refuge Hybrid $159 12.3 oz. VerticalX (60g) 20D x 30D Yes
Patagonia Nano-Air Hoody $299 12.2 oz. FullRange (60g) 33D Yes

The Competition

We love the Atom SL Hoody for its solid weather protection, light weight, and versatility. In the synthetic jacket market, one of the Atom SL’s closest competitors comes from in house: the Proton FL Hoody. The Proton is purpose-built for alpine and rock climbing with a competitive 11.4-ounce weight, thin 20-denier shell fabric, and light dose of Octa Loft insulation. Stacked up, the Atom SL is warmer and offers better protection against wind and water (with the exception of the side panels). That said, the Proton is the much better breather, making it the superior choice for high-output use.Arc'teryx Atom SL Hoody synthetic jacket (interior weave)

Another ultralight piece from Arc’teryx to have on your radar is the Nuclei FL. Right off the bat, we’ll note that this jacket offers significantly more warmth than the Atom SL with lofty 65-gram Coreloft Continuous throughout. It’s also a little heavier at 11.5 ounces but more delicate with a 10-denier face fabric (for more, see our in-depth Nuclei FL review). Both jackets are tuned for climbing but fall into different categories: the Nuclei is a great belay jacket for shoulder seasons or cooler days, while the Atom SL is the better wind blocker and all-around option for stop-and-go activities.

Outdoor Research’s Refuge Hybrid offers the most similar design to the Atom SL, with insulation only around the core, thin fabric over the arms, and stretchy fleece at the sides. However, the Refuge runs a bit warmer than the Atom SL with 60-gram insulation (the Atom SL uses 40g) and is heavier at 12.3 ounces. Both are decently mobile, but the Arc’teryx has a better fit (the OR is much boxier) and is the superior ultralight and packable option, while the Refuge is a better breather and substantially cheaper at $159. In the end, a final decision will come down to how you prioritize cost, styling, and weight.Arc'teryx Atom SL Hoody synthetic jacket (hiking in forest)

Finally, Patagonia has discontinued their Nano-Air Light Hybrid, which was a closer competitor to the Atom SL, but their standard Nano-Air Hoody remains a standout in the active insulation market. Comparing the two, the Nano-Air is quite a bit warmer with 60-gram synthetic used throughout, and its breathable shell fabric and lining means it’s a slightly better ventilator. However, the Atom SL easily wins out in weight and packability (the Nano-Air is considerably heavier at 12.2 oz.), while providing better outright wind and wet-weather protection. But as a daily piece that can take you deep into the backcountry, the Nano-Air is hard to beat, which is why it’s consistently been one of our top-rated synthetic jackets and midlayers.

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