The Thorium AR does exactly what it intends to, which…

Rating: rated 5 of 5 stars
Source: bought it new
Price Paid: 230 CAD


The Thorium AR does exactly what it intends to, which is keep you very very warm and comfortable for a low weight penalty. Buy this jacket if you want a near a perfect insulation layer for weather below -5°C (23°F) that packs small and feels like wearing a cloud.


  • Extremely warm (best use is below -5C/23F)
  • Excellent cut and articulation
  • Packs small, weighs little
  • Ridiculously comfortable


  • Too warm above -5C/23F
  • Works best as part of a system

First things first, this jacket excels at its intended use. If it's cold but dry, it's great. If it's wet or the wind picks up you WILL need a shell over it (down + water = bad, it isn't incredibly wind resistant). It's designed to be worn over a baselayer and under a shell, during low to no activity. If you're huffing up a mountain you'll need to take it off and rely on your shell and baselayer. It's designed to keep you warm when you stop for a break, make camp, or are in -25C/-13F and below. Basically if you're sweating, take it off, if you're cold put it on.

Also of note, this won't keep much of your butt or legs warm. If you're out in weather cold enough to need this you should have two layers on your legs (two out of three of long johns, pant, or soft/hard shell), or on a short fair weather commute with only a t-shirt on under it.

City commute (20min walk, 20min waiting for bus, 20min walk):
-30°C/-22°F and above with only a t-shirt on under it, along with toque, mitts, and windshell pants and I'm toasty. If it's colder, or wet, I throw a shell on over it. It is really, really warm. -30°C-ish with only a t-shirt under is pretty impressive.

  • Above -15C/5F I wear it with jeans and a T-shirt. 
  • Above -5C/23F I switch to my shell and a light fleece.

In the backcountry, I wear a baselayer and shell on the go, and add this when I stop or the temp drops significantly and I'm too cold in the shell/baselayer. It comes with me and works perfectly from -5C/23F down to -40C/-40F, working alongside mitts, toque, long johns, shell pants, a 200wt merino baselayer, and a hardshell jacket. I carry a (very) light fleece for on the go hiking as well if weather requires it, as the Thorium doesn't breathe very well for high output activity.

To my knowledge it's one of the warmest for the weight on the market, and strikes a perfect balance for really cold areas. Lighter puffies tend to be a bit too cold to use with only a shell and baselayer (or T-shirt in town). Heavier jackets are pointless, as this is warm enough for a -30C/-22F hour long belay with shell over it. If you live somewhere where it rarely/never drops below -10C/14F, maybe look for a lighter puffy, or aim for a fleece.

Awesome. I'm about 5'11" (180cm), and 160 lbs with long arms and shoulders somewhere between beanpole and broad. The fit is near perfect, with full range of movement and no pulling.

The sleeves are long enough and stay put with a well designed elastic cuff (I was surprised how much I like it, figured it wouldn't be as good as adjustable velcro cuffs).

The hood is snug and mostly stays out of your line of sight. It is very warm, and fits ok under a helmet. Once zipped all the way up it stays put without any adjustment. Not keen on the fact that the hood can't be pulled on/off without unzipping, but that's a pretty minor annoyance.

The bottom has an elastic pull to block out drafts, which works as intended. Between the cuffs, bottom elastic draw, and collar you'll be in a toasty cocoon with no drafts.

The zippers are smooth and high quality, and I've yet to have them catch.

It suffers from same problem all men's outdoors wear seems to have, which is enough material/zipper to cover a beer gut if you happen to have one. This leads to a slight "zipper paunch" which is mildly annoying if you're skinny. Arc'teryx's stuff seems to be a bit trimmer than its competitors though, and it isn't as pronounced in this jacket as most others I've tried. It's definitely one of the trimmest I've worn with exactly enough excess material. If you have a beer gut, it's great aha.

The jacket layers exceptionally well, with room below it without being too boxy/bit. It fits nicely under a shell, and has slick enough fabric that your layers won't bind.

I've had this puffy for three years, and it's one of my favorite pieces of clothing/gear. It's so comfy you're actually excited when you get to wear it. The attention to detail is also incredible, every stitch is perfect. I love this jacket in a way you can't understand until you've owned a really high quality puffy.

Weather proofing/breathability:
While it's great on its own on clear days, if you see clouds you'd best bring a shell. It can resist a bit of drizzle or snow, but not for prolonged periods. If it gets wet you're in trouble, so don't go swimming in it.

The puffy breathes better than I have any right to expect, but you certainly won't be hiking in it for more than a few minutes. If you're sweating you'll have to take it off, or end up swampy. It's a bit unpleasant against bare wet skin as well.

It is not intended to be worn on the go though, so these shouldn't be real issues...

It isn't made of iron, but you don't have to baby it either. The fabric is waaay tougher than you'd think when you hold it. No holes yet. That being said, keep it way away from fire, or well protected under a shell. Sparks will burn instant holes, through which you'll quickly lose down. After three years of heavy use (daily commute during the winter, plus snowshoeing and mountain hiking on most weekends).

Packs down to smaller than a Nalgene bottle into its own pocket. It weighs next to nothing. The pockets are big enough to store your gloves, but are a bit tight for large mitts (they will fit without jamming them in though). It's more than worth its weight when winter hiking, even if you're aiming for that ultralight baseweight.

Lighter puffies are not warm enough in my opinion (if you're warm enough that a lighter puffy is enough, a light fleece, baselayer, and a shell should be enough (in which case they also breathe better than a puffy). This puffy is perfect for its purpose. This jacket is as good or better quality than everything on the market. I spent a lot of time shopping around, and talking to fellow outdoor enthusiasts. Happy to say it was the right choice.

If you're an active outdoors sort, it is very much worth investing in a high quality puffy like the Thorium AR, and  high quality baselayers (long johns and long sleeve top). These are three places you will never, ever, regret spending extra money (even if you're a cheap-wad like me).

Disclaimer: I got this for 40% off at a retail store as part of an inventory shift event. It's pretty pricey at full price. That being said, if it was stolen, I would immediately buy a new one to replace it, even at full price. Even someone as stingy as me is willing to spend for this quality.


Welcome to Trailspace, James. Thanks for the thorough review. Do you have any pictures of your hoody you could share?

1 year ago

Nice review, James! Thanks for taking the time to share it on Trailspace. I'd also love to see some pictures in your review.

1 year ago

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