Pro-Tec's Old School Cert Helmet was modified from their original 1973 Full-Tec design, still boasting that iconic retro shape and style that sits low on the head to feel more secure. The shell is constructed from high-impact ABS with an impact absorbing EPS foam liner designed to offer maximum protection against slams. The premium heat-sealed liner keeps you comfortable with an eleven vent design to vent out hot air and let cool air in. The Pro-Tec Old School Helmet complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older. Sizing: X-Small: 52 - 54cm Small: 54 - 56cm Medium: 56 - 58cm Large: 58 - 60cm X-Large: 60 - 62cm