This is your next-to-skin layer, the first layer you put on in the First Lite System. True to Size: Purchase your normal size to wear under other layers. 17.5 micron, ultrafine First Lite Aerowool Fabric featuring 37.5 by Cocona Active Particle Technology. Aerowool is naturally antibacterial, meaning there is no treatment necessary to retain its odor resistant quality even when used for several days in a row. Aerowool is designed specifically to keep you dry and comfortable in high exertion or high temperature environments and activities. Aerowool mesh vent panels maximizes ventilation. Flat lock seams for next-to-skin comfort. Available in men's sizes: SM, MD, LG, XL, XXL. Covered by First Lite's Warranty. Black Finish