UA Microthread technology in the fabric dries faster, won't cling to you, won't chafe & stretches without absorbing sweat. Material wicks sweat & dries really fast. 4-way stretch construction moves better in every direction . Ergonomic flatlock seams allow you to move free without fear of chafing. Shaped hem delivers enhanced coverage without looking big & bulky. Classic racer back unlocks amazing range of motion. Reflective logos deliver greater visibility on low-light runs.