Helmet Sizes: Small: 20.9-21.7inch / 53-55CMMedium: 21.7-22.4inch / 55-57cmLarge: 21.4”-23.2”inch / 57-59cmFeature: ABS hard shellEPS Inner FoamComfortable Inner Pads11 Vents for extra breathabilityComplies with CPSC 16 CFR Part 1203 standardLightweight Only weight :1lb (16oz)Adjustable chin strap with side release buckleSuitable Sports: BikingSkateboardingCyclingRollerbladeLongboardHoverboardScooterSkatingBMX bikingInline & roller skatingOther outdoor activitiesFits ages 5 and olderSuitable users Adult / Men / Women / Youth