To ensure a perfect fit, measure the circumference of your head starting in the middle of your forehead and match it with the sizes below. * XS 20.10 in - 20.50 in. S 20.60 in - 21.30 in. M 21.40 in - 22.00 in L 22.10 in - 22.90 in. XL 23.00 in - 24.00 in. * Multi-impact Design - SweatsaverTM liner comes standard - Adjustable Straps - Triple Eight Customized Logo Rivets * Ideal for skateboarding, in-line skating ("rollerblading"), roller derby, and scooters. This helmet is not for bicycle use. * This helmet does not comply with the U.S. CPSC safety standard for bicycle helmets for persons age 5 years and older and therefore cannot be shipped to customers in California.