Super-light HeatGear fabric delivers superior coverage without weighing you down Mesh underarm & back panels for strategic ventilation Material wicks sweat & dries really fast Anti-odor technology prevents the growth of odor-causing microbes Ergonomic design keeps seams off high abrasion areas & increases durability Hybrid raglan sleeve construction for added range of motion & comfort HeatGear Armour is UA's original performance baselayer - the one you put on first and take off last. So they made it extra comfortable by wicking sweat and stretching so you can move no matter what.