What Our Gearhead(R) Experts Are Saying: "This is my go-to layer for fast-moving days in the mountains. The combination of Primaloft Gold Active and Airmesh lining keeps you warm without overheating. I love how it vents under the arms when I'm pushing hard and still traps heat when I stop. Super versatile and packs down small." When you're chasing altitude gains or racking up pitches, the Mountain Hardwear Kor Alloy Jacket keeps you perfectly balanced between warmth and breathability. The lightweight Pertex(R) Quantum Air shell blocks wind without feeling clammy, while Primaloft(R) Gold Active insulation and Airmesh(TM) lining work together to release excess heat when you're moving fast and lock it in when you pause to take in the view. Underarm panels made with highly air-permeable fabric let you stay comfortable even on steep, sustained climbs. From the kangaroo pocket that doubles as a stash pouch to the stretch cuffs that seal out drafts, every detail is built for serious missions. Whether layered under a shell or worn solo, the Kor Alloy is a dialed piece that adapts as quickly as you do.