The Series exclusive Heatwave skull cap features a kinetic heat return system. The first dual stage heating system for head, hands and feet. The revolutionary heatwave process converts emitted kinetic energy into increased heat that reflects radiated heat back for more warmth. 83% polyester / 17% spandex For winter, hat Flat seams to avoid chafing. 4 way stretch Construction Fit form under a helmet Durable, with reinforced seams.​​