Under Armour Men's Heatgear Sonic Compression Short Sleeve Shirt 100% Polyester Imported Smooth Fabric - An ultra-soft and smmooth fabric that provides extreme comfort with very little weight. 4-Way Stretch Fabrication - Allows greater mobility and maintains shape. Signature Moisture Transport System - Wicks sweat away from the body, keeping you cooler and drier. Anti-Odour Technology - Prevents the growth of odour causing microbes. Smooth Flat Lock Seams - Allow a full range of motion without chaffing.