Tesla CLSL TM-R13-BKRZ_Large Men's Short Sleeve T-Shirt Cool Dry Compression Baselayer R13 We strongly recommend ordering ONE size up what you normally wear. TeslaGears R13designed for all seasons (Releases heat and wicks moisture with a cooling effect) 87% Polyester-13% Spandex Non abrasion fabric material with excellent elasticity and durability Moisture Sensing/Quick time Dry/TWO-WAY Air Circulation.