Breathability Let the air in. That’s the philosophy behind the Arc'teryx Proton, and it works. The jacket’s water-resistant shell, synthetic insulation, and lining are all made with an air-permeable, open structure that helps release body heat when you’re working hard. Proof that it works: On a 23-day Denali expedition, our tester never took the Proton off in temps ranging from -40°F to 40°F. Caveat: Since it lets wind through, it can get chilly if you aren’t moving; keep a shell handy.
Features Exterior hem cords are easy to grab, and the hood cinches down perfectly around heads and helmets with just one adjustment. The No Slip Zip puts little speed bumps in the top of the zipper track to prevent it from opening up as you move, but the tiny pulls are hard to grasp while wearing gloves. The wrist gaiters are a nice touch. m’s XS-XL, w’s XS-XL