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). To determine proper size, measure around head with a soft tape measure or string. Sweatsaver liners should be used to further customize the fit. Manufacturer?s 180-day limited warranty.