Bern Unlimited Watts EPS Summer Hatstyle Helmet 22 1/2 - 24 in Thinshell EPS foam with ABS outer shell gives a durable and long lasting, low profile fit Hard Visor design is well ventilated for a total package of safety, comfort and style Crank Fit dial on back of helmet quickly secures or loosens the fit around your head, super easy to adjust - even on the fly Meets Safety Certification ASTM F 2040, CPSC and EN 1078 and WINTER UPGRADE KIT AVAILABLE SEPARATELY