UNDER ARMOUR. 1316935-001. MENS TACTICAL MOCK BASE LONG SLEEVE T-SHIRT. BLACK. Fitted Next-to-skin without the squeeze. ColdGear Reactor is intelligent insulation that adapts to your activity level for the right breathability and warmth for what you re doing. Fabric has soft brushed nodes next-to-skin for the right warmth that breathes as you move. Material wicks sweat and dries really fast. Anti-odor technology prevents the growth of odor-causing microbes. Mock neck construction for added coverage. 86 percent Polyester with 14 percent Elastane.