Protect yourself while declaring your Team or Driver allegiance. Complies CPSC Safety Standard bicycle helmet for person(s) age 5 and older. Supplied with adjustable padding. Usages include cycling, skateboarding, roller blading, and snowboarding. Diameter Sizing: Small 19" -20 1/4" 48-51cm, Medium 20 1/2" - 21 1/2" 52-55cm, Large 21 3/4" - 22 3/4" 56-58cm.