Triple 8s 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. Two different sized sets of washable, moisture-wicking, stink-free Sweatsaver liners are included. The Triple 8 The Certified Sweatsaver Helmet is available in four sizes to fit kids, youth, and adults: XS/S fits 2021.25 in (5154 cm), S/M fits 2122.5 in (5357 cm), L/XL fits 22.523.5 in (5760 cm), XL/XXL fits 23.524.5 in (6063 cm). CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Older and ASTM F-1492 Skate safety standards. To determine the proper size, measure around the head with a soft tape measure or string. Expect to wear it for a couple of hours before the helmet is completely broken in.