Liquid Force Helmets offer top-notch protection and the market's most comfortable water helmet liner technology. Feature high-density ABS outer shell and a dual-density closed-cell EVA foam liner that does not absorb water. The exclusive Pro-Dri Plus lining wicks away moisture and provides a comfortable fit without pressure points or rubbing. The Flash Helmet has a sweat saver terry cloth liner and removable ear flaps. Sizes (head circumference at forehead): XS(20" - 20-3/4"), S(20-3/4" - 21-1/4"), M(21-1/4" - 22"), L(22" - 23"), XL(23" - 24").