Dual-certified helmet designed specifically for roller derby, with visor made of CE-certified impact-resistant polycarbonate with anti-scratch and anti-fog coatings Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older and ASTM F-1492 Skate safety standards Includes two different sets of removable, washable, terrycloth Sweatsaver liners to customize fit; adjustable helmet strap with side-release buckle Available in four sizes: XS/S fits 20 – 21.25 in (51 – 54 cm), S/M fits 21 – 22.5 in (53 – 57 cm), L/XL fits 22.5 – 23.5 in (57 – 60 cm), XL/XXL fits 23.5 – 24.5 in (60 – 63 cm) To determine proper size, measure around head with a soft tape measure or string; liners should be used to further customize fit