DOT Approved; L (53-54 CM,20.9/21.3 Inch) Light weight durable aerodynamic thermoplastic alloy shell Heavily cushioned and comfortable interior Beautiful glossy UV protective finish Removable and washable padding Helmet Size Chart

S 49-50 CM 19.3/19.7 Inch
M 51-52 CM 20.1/20.5 Inch
L 53-54 CM 20.9/21.3 Inch
Helmet Size Tips

(1)Wrap a measuring tape around your head about a half-inch above eyebrows
(2)Take measurement two to three times to pick the largest one.