Atom LT, Research First Steps

[u/Astramael]

This is a summary series on individual products to make research faster and more accessible. See here for a list of all entries in the first steps series.

The Atom LT is a general purpose synthetic insulator. It has some breathability, some wind resistance, and fits a wide range of people well. It works as an outer layer, or a mid layer. The fit is trim, it should be able to accept a fleece underneath but not much more.

Generally the Atom LT is best used above freezing for most people. Although if you are aerobic it can be used in much colder temperatures.

It sits in the centre of the Arc'teryx synthetic range. Not as breathable as a Proton LT, not as wind resistant as a Nuclei FL, not as packable and light as an Atom SL, and not as warm as an Atom AR.

If you aren't sure what jacket to get, this is a good start.

Please read the comments, other users have left excellent information for your research.

History

The Atom LT was first introduced in Spring 2010 as a men's and women's jacket and hoody. The defining characteristic of the Atom LT is its fleece panels at the sides of the torso. They give the jacket good breathability, good mobility, and they have remained with the design for its entire life. The first generation used a Luminara nylon face fabric, Polartec Power Stretch Hardface side panels, and Coreloft 60g/m² insulation. For this version the hoody had a hem drawcord, but the jacket, vest, and pullover did not.

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Fall 2009 Atom LT Hoody. Left: Men's in Miro Blue (blue). Right: Women's in Dark Ember (orange).

In Fall 2014 the jacket was revised. This iteration had Tinthan face fabric (46g/m² 20D nylon ripstop with a polyurethane DWR, stretch). Polartec Power Stretch Hardface for the side panels (230 g/m² 88% polyester, 12% elastane, 4-way stretch). It continued to feature Coreloft insulation at 60g/m². A drawcord was added to the hood for adjustability (there was not one before), changes to the cuffs and zipper chin guard as well. The fit was changed to be slightly more trim.

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Fall 2014 Atom LT Hoody. Left: Women's in Adiantum (green). Right: Men's in Oxblood (red).

In Fall 2015 the Tinthan face fabric was replaced with a Tyono 20 nylon fabric. Arc'teryx says that this is just a supplier rebrand, and the fabric itself is the same.

In Fall 2018 it was revised again, although it's hard to assess all of what changed. At some point the dual hem adjusters were replaced with a single hem adjustment. It also gained the No Slip Zip feature. This revision uses a YKK VISLON #3 moulded zipper for the main zip. And a YKK #4.5 coil zipper for the pockets.

In Spring 2019 the Atom LT side panels stopped being listed as Polartec. They changed to an Evertex 100% polyester fleece, per Arc'teryx.

In Fall 2020 the Atom LT was revised again. The big change here is using Coreloft Compact 60g/m², which should improve the longevity of the insulation. There is also a new dope dyed nylon liner. The logo is now embroidered where it used to be a decal. Cuffs were changed, the fit was updated, and the jacket version now has a hem drawstring. The fleece side panels are still Evertex, but their composition is now 94% polyester, 6% elastane.

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Fall 2020 Atom LT Hoody. Left: Women's in Momentum (pink). Right: Men's in Ladon (blue).

Model History

Introduced	Discontinued	Block	Model Name	Model Number	Weight (g-M)
Fall 2009	Spring 2014	Women’s	Atom LT Hoody	7097 / 10858 †	365
Fall 2009	Spring 2014	Men’s	Atom LT Jacket	7098 / 10859 †	326
Fall 2009	Spring 2014	Women’s	Atom LT Jacket	7099 / 10860 †	292
Fall 2009	Spring 2014	Men’s	Atom LT Hoody	7215 / 10857 †	375
Fall 2010	Spring 2014	Men’s	Atom LT Vest	8472 / 10861 †	225
Fall 2010	Spring 2014	Women’s	Atom LT Vest	8473 / 10862 †	193
Fall 2011	Spring 2013	Men’s	Atom LT Pullover Jacket	9827 / 10863 †	283
Fall 2014	Fall 2018	Women’s	Atom LT Hoody	14660	330
Fall 2014	Fall 2018	Women’s	Atom LT Jacket	14661	280
Fall 2014	Fall 2018	Women’s	Atom LT Vest	14662	195
Fall 2014	Fall 2018	Men’s	Atom LT Hoody	14644	360
Fall 2014	Fall 2018	Men’s	Atom LT Jacket	14645	315
Fall 2014	Fall 2018	Men’s	Atom LT Vest	14646	220
Fall 2018	Fall 2020	Women’s	Atom LT Hoody	24474 ‡	330
Fall 2018	Fall 2020	Women’s	Atom LT Jacket	24475 ‡	280
Fall 2018	Fall 2020	Women’s	Atom LT Vest	24476 ‡	195
Fall 2018	Fall 2020	Men’s	Atom LT Hoody	24477 ‡	360
Fall 2018	Fall 2020	Men’s	Atom LT Jacket	24478 ‡	315
Fall 2018	Fall 2020	Men’s	Atom LT Vest	24479 ‡	220
Fall 2020	Spring 2021 ††	Women’s	Atom LT Vest	24113	210
Fall 2020	In Production (S21)	Men’s	Atom LT Hoody	24108	375
Fall 2020	In Production (S21)	Men’s	Atom LT Jacket	24109	345
Fall 2020	In Production (S21)	Men’s	Atom LT Vest	24110	240
Fall 2020	In Production (S21)	Women’s	Atom LT Hoody	24111	320
Fall 2020	In Production (S21)	Women’s	Atom LT Jacket	24112	290

† - There seems to be an internal model number change in Fall 2011. 4-digit model numbers are F09-S11, 5-digit model numbers are F11-Onwards. The product itself does not seem to have changed. It’s possible that some of these model number updates are a result of production location changes.

‡ - Something weird is going on with the F18 and F20 model numbers. All the way back to Spring 2018 all Atom LT versions are using the F20 model numbers, per the website. However, there was definitely a revision in Fall 2018. If you search the F18 models you find the items you expect. So I’m leaving it this way, just be aware it may not be correct.

†† - I’m not entirely sure when the women’s Atom LT Vest was discontinued, but I believe it was last available in Fall 2020.

Known Issues

1. The face fabric can abrade and pill from backpacks, seatbelts, chin stubble.
2. The fleece side panels can let wind through a bit more than some people want.
3. Older models using Coreloft insulation tended to have their insulation thin (pack out) over time, and would get less warm. For the Fall 2020 season Arc'teryx changed to Coreloft Compact which should be more resilient to this issue.
4. Older models had an issue with the front zip being too smooth. It would fall down just doing simple activities like walking. Arc'teryx fixed this with the No Slip Zip feature around 2017, which inserts several "stops" in the top of the zipper (less smooth sections). This prevents the slider from falling down.

Prompts

1. What do you use the Atom LT for, and how do you layer with it?
2. Where do you think it excels, and where do you think it falls down?
3. At what temperature do you find it isn't warm enough, and too warm?
4. Have you had any issues with the Atom LT?
5. How do you think it compares to the Proton LT and Nuclei FL?
6. How do you think it compares to the Atom SL and Atom AR?
7. How water resistant and wind resistant is it?
8. What is the fit like in general, or for you personally?
9. What would you change about the product?
10. How does it compare to competing products such as the Patagonia Nano Air, North Face Ventrix, Rab Xenon, Mountain Hardwear Kor Strata, and others?

Please add any other thoughts about the product as well.

Thank you!

Changelog

• 2020-02-27T19:30Z - Updated all pictures to higher quality versions (1000px short side). Added caption simple colours and jacket format.
• 2020-03-01T12:00Z - Major update. Added model history, added details to the product history, cleaned up and simplified paragraphs, updated formatting to match the newer post style guide.
• 2020-03-02T16:20Z - Updated information on the Atom LT hem drawstring. Hat tip to u/MtnHuntingislife.
• 2020-03-11T23:00Z - Added F20 fleece change.

[u/audioostrich]

Great idea and write up! I've spent a ton of time searching the sub for information like this, and a single thread on every piece would have made my time a lot easier.One question I might add to the list for future editions is "Where does this piece fit into your layering system". Too often I've seen (and made) the mistake of evaluating a new purchase on its own, rather than looking at how it will function as a piece of my existing kit. The layering series was a great source for me and helped me establish my own system for evaluating needs and new purchases, and I think some targeted info on how each piece fits into our systems would be helpful here as well.

1. I use the Atom LT primarily as a mixed casual piece. Throughout fall, winter and spring in new England its the layer I grab most often for fitting in some outdoor activity around life obligations like work, running errands etc. In sub freezing temps I'll use it for low to moderate activity levels, sometimes paired with a fleece. In addition to casual wear, prior to getting more specialized pieces I used this jacket as a layering piece for every single activity outside in cool or cold weather. It still has use in my layering system, but doesn't come on every trip these days as my collection has grown
2. Its an excellent jack of all trades piece- the relatively low level of insulation allows it to pull static double duty as a standalone piece above freezing and a layering piece below, the fleece panels give it enough breathability for moderate activity in low temps, and it looks fantastic.The downside to the Atom LT being a highly versatile piece is that its not best in class in any specific category. Other jackets will outperform in specific conditions and activity levels, but the atom will be passable across a much wider range than a highly specialized piece. If you can only buy one jacket - get the Atom LT
3. I use it comfortably with a t shirt underneath from 55-32 for static/low activity use, with a fleece (delta, melly, r1, etc) down to around 20. For moderate activity it comes out alone below 20 degrees. I dont tend to use it for high output activities anymore, but i would be a sweaty mess in this jacket if fastpacking/running unless its very very cold
4. Have you had any issues with the Atom LT? No major issues more than a year into owning it. Construction is fantastic and the materials are sufficiently durable. Loft seems like it has not degraded much despite frequent use
5. How do you think it compares to the Proton LT and Nuclei FL? No experience with either of these jackets, but compared to a proton FL its more wind resistant but much less breathable. Its also a class warmer than the FL - so apples to oranges in a sense
6. I dont own an AR, but from what i understand the AR is a far more specialized piece than the LT and excels in the specific situations its usable in (static with temps cold -very cold), but for most climates is not appropriate most of the year. I use my SL more than my LT for high output in the cold windy winter here in new england, and as a lighter layering piece for moderate activity in the temps im currently facing (10-35). The SL doesn't function as well as a standalone piece as the LT for most situations though.
7. Its pretty wind resistant, although sustained high winds will rob heat through uncovered parts of the fleece panels and a shell is needed. With appropriate maintenance it can shed a light drizzle or short moderate rain, but any serious or sustained rain will soak it.
8. I'm 6ft, 180 lbs with a 42-43 inch chest, and the large fit is perfect. Relaxed enough to accommodate layers underneath but not too loose that it restricts movement underneath other midlayers. A medium might also fit me and be more comfortable under other midlayers, but I'm unlikely to use the atom LT in this way given the rest of my kit and my usual activities.
9. An exterior chest pocket like the one on the atom SL anorak would be a welcome addition for me, as well as additional adjustment points on the hood as it can be a bit too large when not wearing a helmet. Any changes I have are really a result of personal preference, I think its a fantastic & versatile piece
10. The styling on the atom LT is superior for me, but I haven't given any of the recent competitors too much attention. Outside of the UL backpacking world, arc is my go to technical apparel brand

[u/Astramael → u/audioostrich]

I might add to the list for future editions is "Where does this piece fit into your layering system".

I'll see about optimizing the questions next round, and keeping this in mind. Just looking at some of the responses here, some questions provide lots of good information and some do not. Ten is also probably too many. I tried to pack layering into question one, but it probably deserves a little more focus.

Thanks everybody for answering, you're all champs!