Mountain Hardwear Men's Kor AirShell Warm JacketMountain Hardwear Men's Kor AirShell Warm Jacket Change is good. But changing layers every five minutes? We have better things to do. With a soft airmesh lining on the inside, and breathable, abrasion resistant Pertex Quantum Air stretch fabric on the outside, the Kor Airshell Warm Jacket is a dynamic duo of technical performance. The jacket's active insulation keeps you warm and fends off wind and light moisture while remaining incredibly breathable,