The Mountain Hardwear Advance Lightweight Zip T is a lightweight and comfortable base layer made to keep you dry. Channeled construction increases performance and decreases weight. 100% polyester material wicks sweat away from your skin, breathes and dries quickly, while Chitosan anti-microbial finish controls odor. The Advance's seams stay clear of high-abrasion areas, so you won't get pressure points from wearing a backpack.