The Under Armour Boy's Coldgear Infrared Everyday Crew is the baselayer you'll never want to take off?it feels like your T-shirt, only warmer. That's because the ColdGear® Infrared technology holds just the right amount of extra heat without adding any weight or bulk. IT is made with a 4 way stretch fabrication that gives you a full range of movement. It uses Under Armour's signature moisture transport system to wick away sweat. The anti-odor technology prevents the growth of odor causing microbes.