The core base layer is designed to regulate your body temperature at the base level through all weather conditions. The body-mapped design has been athletically shaped, so the high wicking fabric can sit tight to the body in order to absorb and disperse as much sweat as possible, all the while allowing maximum movement in the high stretch areas. The unique heat control technology means that although the core has incredible warmth properties while worn under a mid layer, it also has the ability to cool rapidly when exposed to external air.