Triple 8?s THE Certified Sweatsaver Helmet for Skateboarding, BMX, Roller Skating, and Action Sports offers comfort and safety with high impact-absorbing EPS foam and thick dual-density soft foam Triple 8 Sweatsaver fabric liners. Dual-certified to comply with US CPSC bike and ASTM F-1492 skate safety standards, it?s the ideal helmet for biking, skateboarding, skating, roller derby, scooters, BMX, and other action sports. Two sets of moisture-wicking, stink-free Sweatsaver liners in two different sizes are included?mix and match for a customized fit. The plush terrycloth liners attach with hook and loop tape and can be removed for washing. Chin strap is adjustable and fastens with a side release squeeze buckle. The Triple Eight THE Certified Sweatsaver Helmet is available in four sizes to fit kids, youth, and adults: 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). Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older and ASTM F-1492 Skate safety standards. To determine proper size, measure around head with a soft tape measure or string.