Under Armour's Base 2.0 is built to keep you warmer and dryer than ever in cold conditions. This base layer traps heat with cozy grid fabric against the skin, while the smooth outer surface lets you layer with ease. . Midweight UA Base 2.0 made from polyester and elastane highly versatile protection for colder conditions and a variety of activity levels. Fitted: Sits close to the skin for a streamlined fit without the squeeze of compression. Soft, brushed negative grid interior traps heat in tiny pockets, providing superior warmth without weighing you down. Smooth outer surface makes it easy to add layers. 4 way stretch fabrication allows greater mobility, maintains shape, and enhances dry time. Signature Moisture Transport System wicks sweat away from the body to keep you dry and comfortable. Quick dry fabrication keeps you light and comfortable. ArmourBlock anti odor technology prevents the growth of odor causing microbes to keep gear fresher longer. Raglan sleeve construction and flatlock stitching allow a full range of motion without chafing. Ergonomic seam placement for mobility and comfort.