Under Armour Reactor Mens Black T-ShirtUltralight fabric has a unique hex shaped pattern that traps some warmth but still breathes as you run Stretch mesh panels under the arms & across the shoulders for strategic ventilation 95% Polyester, 5% Elasatne Coldgear Reactor Run Short sleeve Shirt Short Sleeve 4 way stretch construction moves better in every direction Material wicks sweat & dries fast Under Armours mission is to make all athletes better through passion, design and the relentless