We sent our mate Pat, on a backcountry mission for a few days to give the latest Arc'teryx Proton LT jacket a run for its money. See how it stacks up in the Aussie alpine. The Proton LT is Arc’teryx’s latest insulated jacket to hit Aus. It’s the more breathable, more technical version of their bestselling Atom LT and I was lucky enough to give it a walloping in the backcountry last week. Proton vs Atom vs Nuclei Before diving into the review, it’s important to know where this jacket sits in the Arc lineup. Arc’teryx has three insulated jackets, the Proton, the Atom and the Nuclei. The Proton is their most breathable version, it’s made for high output sports and can keep you warm while staying nice and breathable. The Atom sits in the middle and is their most popular jacket. It has some DWR (Durable Water Repellent) coating, good wind-blocking abilities and is still reasonably breathable. Finally, the Nuclei has greater water and wind resistance but isn’t as breathable as the Atom or Proton. It is generally for colder weather and lower output (such as belaying between climbs). They also have letters after the jackets to signify their specialities, such as AR, LT and SV. There are a bunch of different names for different usages. I won’t go into detail on those too much but all you need to know is that the Proton is only available in Australia in the LT model and it stands for lightweight, with a 'high performance, minimalist design'. Warmth Warmth is probably the primary reason you bought an insulated jacket, so you’d hope it can at least do that. Well, I’m here to tell you it stands up to the challenge. We had some nights that were below 0°C and it stood up to those nicely. It also did a good job keeping me warm when transitioning and scouting out lines on a windy ridge after the skin up. Although it blocked a decent amount of wind, it’s not made for that and I put on a shell jacket for the runs down and when it really started blowing. The only reason this doesn’t get 10/10 is that I’m sure next year’s will be even better. Breathability Breathability is where the Proton LT starts to shine. I’ll freely admit that I’m a bit of a sweaty boy, and it did a stellar job dumping that moisture and keeping me warm and dry while skinning up some nice inclines. It’s made for these conditions where you’re burning up a climb, working hard, and producing a lot of heat. It’s not perfect (no jacket is) and I still got a bit sweaty, but for its warmth, it’s better than any other insulated jacket I’ve tried. Design I’m generally a big fan of Arc’teryx design and attention to detail. I find their sizing spot on and they are constant tweakers, improving the little things year after year to make incredibly refined gear. In saying that, I’m taking a couple of points off here for the limited colour options they give in Australia. While other countries get the full range, here in Aus we only get black or dark green (men’s) and black or dark red (women’s). Aside from colour options, this jacket is just classic Arc. The hip pockets are still accessible under a pack or climbing harness and I much prefer the outer chest pocket on the Proton LT to the inside one in the Atom LT. While I’ve only used it for skiing so far, it had good articulation and I couldn't imagine it holding you back when doing nice big overhead reache when climbing. Finally, the hood is as good as any other I’ve used. It fits easily over a helmet and can cinch down around your face when it gets cold. It’s clearly designed with technical use in mind, that well and truly shines through! It’s a well thought out jacket and has already become my go-to when planning a couple of upcoming trips. The Verdict Probably the biggest praise that I can give for this jacket is that when wearing it, I almost forgot I had it on. I didn’t overheat too much when working hard and it kept me nice and cosy when taking a break and hanging around. For me, that’s the test of good gear. It shouldn’t take your attention away from the adventure at hand. I was provided with the Arc’teryx Proton LT jacket for review purposes and got to keep it. I have also worked with Arc’teryx as a freelance photographer. These did not influence my review and I am honestly stoked on this jacket.