Under Armour Alter Ego Short Sleeve Compression T-Shirt Second-Skin Fit - Delivers a locked-in feel for optimum muscle performance. HeatGear Fabric - Combined with UA compression makes the top comfortable enough to be worn all day. 4-Way Stretch Fabric - Lets you move freely. Moisture Transport System - Wicks away sweat and keeps you cool and dry. Anti-Odour Technology - Prevents the build up of odour causing microbes.