Arc'teryx Men's Atom LT Jacket

This is a great light jacket or heavy midlayer. It is super light and compressible and way warm. The jacket packs well into its own sleeve when it's in your pack, but the core loft springs back quick and warms up fast. Arc'teryx laminates the core loft right to the face fabric so you don't have baffles keeping the insulation together. This is awesome because after use and abuse the insulation is still in the same place it was when you bought the jacket. Unlike baffled jackets if they get compressed for a long time or after a few years of hard use the insulation stops lofting back out and filling the whole baffle and you get cold spots.
The low profile stretch cuffs work great when layering to reduce bulk around the wrist. And the side stretch panels keep the fit snug.
When wearing the jacket alone those side panels help vent excess heat and they made the zipper with out a stop so one yank at the top of the jacket opens the whole thing up to dump heat fast.
I have used this by its self around town because it's classy looking. I have worn it on the skin track by its self and under my shell at a resort. This is a great piece to own if you live or recreate I the cold.
I'm 6'6" and 170 pounds and the large is perfect

When I first received this jacket, I was a little disappointed by the lack of , well, jacket. It's a very thin jacket. For it's price you would expect something like the Patagonia Down Sweater, which has substantially more girth.
But, after putting it to use, I am absolutely pleased with my purchase. For being a thin, slim fitting jacket, it is VERY warm. I use it as my insulating piece beneath an Arcteryx Theta SV, and the combination is perfect. It does a great job on colder days when temps are below freezing, although if the sun is out, and temps begin to climb at or slightly above freezing, I found the combination Atom LT/Theta SV was almost too warm. That's a good thing, in my opinion, being as I am confident I won't need any extra layers unless the temp REALLY drops.
For sizing purposes, I am 5'11", weight 180, have a 33-34 in waist, and I went with a Medium. The medium is perfect as a slim fitting, layering piece, although if I were to use this as an around-town jacket, I would go with a large for a more casual look. For reference, I wear a medium in the Patagonia Down Sweater, which is a nice, casual fit. So the Atom LT does fit slimmer.
In conclusion- great jacket, great for layering, very pleased

I've owned this jacket just over a year. I wear it everyday from October -March. It is the perfect piece for cold commuting on a bicycle and chilly days to the craig.
I was very skeptical of the Coreloft insulation before I had purchased the jacket, and now I am a believer. It regulates with your body temperature very well. Not quite as good as premium down, but it still works amazingly.
Thinking back on it, I wish I would have gotten the hooded version, but this piece is very nice, but it also passes for looking like casual jacket.
Don't get me wrong, I'm a huge gear whore, but I don't feel the need to have every jacket look like I'm geared up to Summit K2 when I'm going out to dinner.
For sizing, I'm a pretty thin guy. 6'0, 135lbs with an even ape index. And I think it fits very nicely. It's hard to find a medium that actually fits these days.
The only thing I would add would be elastic waist tensioner so the bottom was more form fitting to my actual waist.

Read the reviews. This jacket is awesome. I am not going to give you all the details. You will find them in the glowing reviews listed here and on other websites. I am up to my eyeballs in Arcteryx & Mammut jackets because they are the best overall quality. The Arcteryx Atom lt. is my all time favorite jacket. It is incredibly warm and light and looks outstanding. I have worn this jacket all winter by itself and as layer underneath a gore-shell jacket. It is a very versatile jacket for the spring, fall, and winter seasons. I am an athletic 5'9" at 160lbs and a large fits nice with room for a layer underneath. At the risk of sounding obsessed, I bought the hoody and vest version as well. I love this jacket. It is extremely versatile, light, warm, somewhat breathable, wind & water resistant. PS I bought the vest in medium for snugger fit.

I bought this jacket in 2009 and it remains one of my favorites. It feels great over a wide range of temperatures, say, down to the 20's (if you're active) and up into the 60's. It's light (my medium weighs 12.3 oz) and the trim fit looks great around town AND on the trail. The "Powerstretch panels" do a nice job with ventilation during exertion. Jacket does have an internal chest pocket which is not listed in Product Description above. There's no cinch at the waist hem, but it's stretchy and wind-up-my-back hasn't been a problem. I'm a big fan of the "stretch-knit cuffs" - Arc'teryx chose a sweet fabric and nifty design for this part of the jacket (and the cuffs just feel great on my wrists). I can't recommend this jacket enough.
Pic below shows Atom LT in spitting snow at 11,000 ft in the Wind River Range.

This is a great jacket to add to your collection of Arc'teryx, It's a really LT jacket that you can use in a wide range of temps. I started out in 35 degrees in the morning to 62 degrees in the afternoon. The jacket preformed very well, I was not hot or cold in any of the temp ranges. I was perfectly comfortable. I am amazed. The jacket is a real fashion statement as well, I received many compliments on the jacket itself. I will try this jacket even in lower temps to find its limits. Over all this jacket is made very well, and is very versatile for many different occasions. You won't be disappointed with this jacket.

This is my most grabbed jacket when i leave the house. It just feels cozy and feels like the perfect jacket for a wide variety of Colorado/Utah temps. It's my favorite mid layer for cold weather. It's the perfect weight mid layer under a shell for skiing and under a soft shell for winter hiking. The fleece side panels really help it breath when you're sweating. The styling is plain enough to double as my every day cubical life jacket which makes it easier to justify the price tag.

I am 6 ft 170 lbs and am usually between a medium and large. I went w/ a medium and it is a bit snug but given the lightweight build, I see this a true mid layer so a snug fit is okay. If I wanted a more relaxed fit, I'd go w/ a large. Nice looking jacket and very comfortable w/ the side stretch panels.

All I can say is that mine was a layer for 12 days between basecamp and the summit of Aconcagua, and it was an indispensable piece of lightweight gear. If it can help keep me warm at 20,000+ feet, it's good for lower altitudes and less demanding conditions. Worth it's weight in gold. I like it so much, I have the hooded and the un-hooded versions.

This is a great mid-weight level insulated jacket. It wears well inside a shell for heavy weather. It is a great and light and packable belay jacket. Its hard wearing and can be worn by itself for high output activity. The Large fits great - I'm 6' 170lbs.