Under Armour Lady HeatGear Sonic Racerback Tank Top Vest 90% Polyester, 10% Elastane UA HeatGear Fabric - Wicks away sweat to keep feet cool, dry, and light. Signature Moisture Transport System - Wicks sweat away from the body, keeping you cooler and drier. 4-Way Stretch Fabrication - This lighweight fabric improves mobility and accelerates dry time. Anti-Microbial Technology - Keeps your gear fresher, longer. Smooth Matte Finish - With a technical feel.