This Midlayer Killed My Fleece
The Mountain Hardwear Kor Airshell Warm is our tester’s new favorite layer
Outside's long reads email newsletter features our strongest writing, most ambitious reporting, and award-winning storytelling about the outdoors. Sign up today.
Mountain Hardwear’s Kor Airshell Warm Jacket ($200) confuses me. I’ve been wearing it almost daily for more than two months now, and I still don’t know what it is. Is it a windbreaker? A shell? A midlayer? The more I wear it, the more I realize that it is a little bit of all those things. It was my favorite layer as the weather turned cold and we’ve gone into the heart of winter, single handedly replacing the fleece and light puffy jackets I used to rely on.
I first got my hands on the Kor Airshell Warm on a climbing trip in Wyoming, trying to summit the Grand Teton. During the three-day effort we backpacked five miles in a cold drizzle, then camped at 11,000 feet in the snow. After a 4 A.M. summit push, we were turned around by snow and ice a few hundred feet from the peak, then hiked back down the mountain the following day in fog and light rain. The Kor Airshell Warm was my constant companion. It held off the on-again-off-again drizzle during the approach hike without wetting out. It kept me warm and dry on the bitter-cold summit bid. It served as a comfy mid-layer while hanging out at our high-elevation base camp. I even slept in it each night. I was testing other gear on the Grand Teton too, but the Kor stole the show, doing the job of three other layers (fleece, light puffy, light shell) and saving space in my overstuffed pack in the process.
When I first put on the Kor I thought it was just another lightly-insulated down jacket, but there’s actually no down. It’s insulated with a thin layer of high-loft fleece, which creates air pockets to trap heat and boost insulating properties while adding minimal weight. That fleece is given a mesh liner in certain high sweat zones and the whole thing is wrapped in the outer Pertex Quantum Air fabric, which has a DWR treatment to help battle the elements. I wouldn’t call this a rain jacket—it will get wet in heavy rain, but it proved to be enough of a barrier (without a true shell on over it) during days of wintery mix. That Pertex outer layer is a 20D Ripstop blend of new and recycled nylon that stretches generously and breathes incredibly well, thanks to the openly woven fabric, which allows more air and heat to escape to help regulate your body temperature.
The latter is especially important to me. I sweat profusely and overheating is a constant issue for me in the winter. Mountain Hardwear designed the Kor with that exact problem in mind. It’s built for high-output alpine pursuits where you run the risk of sweating out. Think ice climbing or snowshoeing. In addition to that breathable outer layer, a soft mesh liner helps wick moisture and keeps the interior of the jacket from getting clammy. That liner also means the Kor is a hell of a lot more comfortable than my other super light shells designed for active pursuits. And the jacket is quite light, coming in at 12.3 ounces. It also packs into its own interior pocket, which means it can be thrown into a pack as an afterthought.
One very minor complaint: it’s not the most fashion-forward jacket in my quiver. It’s not ugly, just plain. Still, it’s been a couple of months since my Tetons trip, and yet I can’t quit the Kor. I wear it while I walk the dog on chilly mornings and it’s my go-to layer on cold mountain bike rides. I’m turning to the Kor over my other layers because it does the job without any fuss. It was my go-to fall weather jacket, and now that winter has arrived, I find myself incorporating it into the mix for snowy adventures too. I wore the Kor Airshell as an outer layer on a mild ski day with my kids before the holidays. Then when the temps dropped to single digits, I layered the piece under an 800-fill down jacket. I haven’t had the chance to pull out my skinny skis yet, but I think it will be the perfect outer layer for cross-country ski missions. Just don’t ask me what kind of jacket the Kor Airshell Warm is. Cause I still don’t know—and I don’t care. It just works.