Castelli’s Pro Thermal Women’s Skully provides under helmet warmth that doesn’t intrude on your helmet fit. Constructed with flat-lock stitching, no bulky seams press against the head and a raw-cut edge doesn’t get in the way of helmet straps. Made from thermoflex fabric the skull cap is warm, soft, and stretchy. It also wicks away any excess moisture to keep you comfortable on those long winter rides.