Arc'teryx Atom AR vs. LT vs. SL: Differences and Reviews 2025

Moisture-resistant outer face fabric
Breathable
Lightweight
Compressible and packable
Insulated
Wind resistant

Moisture-resistant outer face fabric
Breathable
Lightweight
Compressible and packable
Insulated
Wind resistant
Versatile

Moisture-wicking
Breathable
Compressible and packable
Insulated
Wind resistant
Ultralight

3. Warmth（AR>LT>SL）

120, 80, and 60g Coreloft insulation

Most synthetic jackets fall on the lightweight end of the spectrum, but Arc’teryx’s Atom AR—along with its successor, the Atom Heavyweight Hoody—is a proper cold-weather piece. The AR uses a combination of 120, 80, and 60g Coreloft insulation that’s strategically “mapped” to maximize warmth—the thicker fill is used in key areas like the shoulders, outer sleeves, and sides, while lighter insulation in places like the underarms helps with venting and keeps weight and bulk in check. Combined with a tall collar, an adjustable, helmet-compatible hood, close-fitting cuffs that provide a nice seal around the wrists, and a very wind-resistant shell, the Atom AR delivers excellent warmth relative to its reasonable, 1-pound-0.8-ounce listed weight.

The AR is a true cold-weather standout and viable down jacket alternative. When worn under a t-shirt or long-sleeve baselayer for low-output activities or daily wear, the jacket’s ideal temperature range is from the low 20s to low 40s. And its reasonably generous fit means it’s easy to add a layer underneath for even colder days.

Source:arcteryx.com

60g Coreloft insulation

The Arc’teryx Atom LT Hoody—along with its successor, the Atom Hoody—has synthetic insulation, so it won’t rival down fill in terms of warmth or packability. But this jacket makes a really nice fall and spring outer layer and also works great as a midlayer for snowsports and in frigid temperatures. It’s filled with 60-gram (g) Coreloft Compact insulation everywhere but the side panels, which are a stretchy midweight fleece. In addition, its weather-resistant shell does a nice job cutting wind, and the tall collar, adjustable hem, and fantastic hood help when you need to hunker down in cold temps.

In terms of warmth, the Atom LT was comfortable down to about 40 degrees Fahrenheit without much in the way of layering underneath. It certainly can go lower with a warm baselayer or if you’re on the move—it was an ideal outer layer on a hike with temperatures hovering in the high 20s Fahrenheit. But for static use, such as sitting around camp when the sun goes down, you need switch to a down jacket or adding a shell overtop.

Source:arcteryx.com

40g Coreloft insulation

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—Generally, you will 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.

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, uninsulated hood rolls and secures with a tab at the back of the neck. 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.

Source:arcteryx.com

4. Weather Protection (AR>LT=SL)

Tyono 30 denier shell with DWR treatment

Arc’teryx bills the Atom AR as either a standalone or midlayer jacket. There are minimal stitches along the exterior, and unlike the lighter-weight Atom Hoody, the side panels are a standard nylon (the standard Atom’s (Atom LT) are fleece, which is an area of weakness in the wind). Combined with a moderately thick, 30-denier (D) outer fabric, the Atom AR has provided impressive wind protection. As expected from a synthetic jacket, the Atom AR is a good performer in the wet, too. The durable water repellent (DWR) coating has easily shed powdery snow and a light wintery mix of sleet and wet snow.

Tyono 20 denier shell with FC0 DWR treatment

Featuring a weather-resistant shell, synthetic insulation, and excellent coverage from its collar and adjustable hood, the Arc'teryx Atom does a nice job in light to moderate precipitation and wind. The Tyono face fabric feels slightly more substantial than other leading synthetics —including Patagonia’s popular Nano-Air—and it’s finished with a DWR treatment that effectively beads up water and snow. Fleece isn't a great wind blocker, so the side panels will let in strong gusts, but its hard-face exterior repels moisture effectively. To be clear, the jacket will start to soak up water in extended rainfall, so it shouldn’t take the place of a waterproof rain jacket or hardshell. But if you do happen to get caught in a surprise storm, the jacket can hold its own for a short period of time. And if water happens to get into the insulation, the good news is that the Coreloft fill will continue to provide warmth (something duck and goose down will not do).

Tyono 20 denier shell with FC0 DWR treatment

Unlike many current active insulation jackets, the Atom SL offers a fair amount of weather resistance. 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 dry 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).

5. Breathability (ST>LT>AR)

Unfortunately, the emphasis on efficient warmth and moderate levels of protection translate to fairly disappointing breathability. The Atom AR’s warmth limits its versatility for higher-output uses (an issue it shares with many down jackets). Arc’teryx has incorporated a panel of their lighter-weight Dope Permeair fabric right under the arms to provide a small boost in breathability. However, the fact remains that this is a very warm jacket that is reluctant to dump heat, and there are far better synthetic options on the market for those looking for a breathable build. Such as Arc’teryx’s Proton series.

One of the compromises of the Atom’s efficient warmth and decent weather resistance is breathability. The Atom runs fairly warm during high-output sports like ski touring. Its face fabric and lining do a good job trapping heat, and while the fleece side panels do help with releasing some hot air, overall ventilation is solidly middle-of-the-road.

It’s common to trade off breathability for weather protection, but the Atom SL manages a really effective balance of the two. The nylon shell isn’t particularly air-permeable (a plus for blocking wind), but the stretch fleece side panels do a good job releasing hot air, particularly during moderate activities like hiking. Those fleece panels extend all the way from the hem to under the arms and wrists, which helps keep you from overheating. Plus, the jacket’s minimalist insulation and mesh lining in the arms keep it from feeling uncomfortable and clammy. That said, the Atom can’t match Arc’teryx’s own Proton FL in outright breathability, but for an insulated jacket that’s still decently weather-resistant, the Atom SL gets solid marks here.

6. Weight and Packability (ST>LT>AR)

	Atom AR	Atom LT	Atom SL
Weight	475g / 1 lb 0.8 oz	370g / 13.1 oz	269g / 9.5 oz

Atom AR Hoody listed weight of 1 pound 0.8 ounces (The latest Atom Heavyweight shares the same weight spec). Relative to the warmth it provides, this is a pretty darn lightweight piece. As expected, the AR (and newer Heavyweight) is noticeably heavier than lightweight and less-warm synthetic models like the Arc’teryx Atom Hoody (13.1 oz.), and Proton Hoody (14.1 oz.). In terms of packability, the Atom doesn’t include a stuff sack or dedicated pocket but can be rolled and compressed into its own hood. The size is pretty substantial—it’s a bit bigger than an American football.
The new Atom Hoody listed weight of 13.1 oz. and perfectly reasonable to haul around in a pack. Unfortunately, the Atom doesn’t come with a stuff sack, nor is it designed to fit into one of its own pockets. Many users wind up rolling the jacket into its hood to toss into a backpack or suitcase for travel. When stuffed down this way and with the hood cinched, men’s medium is roughly the size of an American football (squeezing it in a bag will make it a little smaller).
The “SL” in the Atom’s name is short for superlight, with a 9.5-ounce weight (which is an exact match to its listed weight). This puts it well under the rest of the Atom lineup: the LT (“lightweight”) is 13.2 ounces while the AR (“all round”) clocks in at 1 pound even, although both options are significantly warmer with insulation throughout the entire build. As expected, the Atom SL is quite packable too, although many users 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. Fully compressed, the jacket is about the size of a large grapefruit, and it’s easy to fit into just about any pack.

7. Comfort (AR=LT=SL)

AR provides similar levels of sleeping bag-like coziness. It’s the kind of jacket that makes you happy to throw it on: The interior lining is smooth but noticeably supple—a far cry from the slippery feeling of many lightweight down or synthetic insulated jackets—and the lofty warmth and solid protection provide a nice barrier from the elements. And as expected from Arc’teryx, all the touch points are soft and thoughtfully designed. The cuffs have a nice amount of stretch but stay in place when you add or remove layers, there’s fleece along the back of your hands when you dip them into the outer pockets, and even the shell fabric is reasonably soft and has a high-end feel (a plus because that shell material covers the inside of the collar).

Comfort is the area where the Arc'teryx Atom excels most. You can wear it hiking or climbing and then to the grocery store or bar afterward, all without missing a beat. The interior lining is soft and smooth to the touch, the stretchy sides and relatively athletic cut give it fantastic mobility, and the Coreloft insulation creates a pillow-like barrier from the outside world. Tack on thoughtful touches like a fleece-like lining inside the hand pockets (for the back of your hands) and smooth cuffs, and the Atom is one of the coziest and most versatile jackets.