For those who arn't familiar with the airvantage system, it's a gore system that allows you to blow air into your jacket. After the air is warmed by your body heat, the air (being the best insulator) will keep you warm for hours without the added bulkiness of regular insulation. I have two airvantage jackets and love them. No affliliation with dshack. Just thought I'd share my 2cents. Cuz this system really Kicks A$$.