Great for mountainside activities - no matter how tough. It's a hybrid mid layer that's made with a stretchy knit fabric with micro-grid backer, then body mapped and packed with high-loft QuadFusion™ ƞ. As a result, it's warming and effective, as well as comfortable. No shoulder seams - reducing the risk of chafing against the rest of your gear. Thumbholes on the cuffs help keep it in place and add to the comfort level.