Solid, safe, and certified for bike use, the Entity will help put your mind at ease when you send your little ripper out on the hill or send them off to school in the morning. Let them explore the mountain with confidence thanks to this secure and comfortable helmet. HARD SHELL CONSTRUCTION: Hard-shell helmets are built to last and will look great no matter how many trips they make in and out of your gear bag. Hard-shell helmets protect users from impact thanks to lightweight EPS foam bonded to a durable, injection-molded ABS shell. PASSIVE CHANNEL VENTING: Channels on the inside surface of the EPS direct air-flow between your head and the helmet, removing moisture and excess heat for all day comfort. FULL WRAP LINER: A comfortable, washable, full-coverage, and breathable liner design wicks moisture to prevent overheating and seamlessly integrates K2's fit and audio systems. K2DIALED™ FIT SYSTEM: The K2Dialed™ Fit System creates a custom-fitting helmet no matter what your head shape is. An ergonomically inspired three-point adjustable interface maximizes fit and customization with the twist of a dial. This allows for the ultimate convenience of being able to make fit adjustments on the fly. SNOW CERTIFIED (F2040 + EN1077): Exceeds the US standard ASTM F2040 Standard Specification for Helmets Used for Recreational Snow Sports and the European standard EN 1077 Helmets for alpine skiers and snowboarders. BIKE CERTIFIED (CPSC + EN): Certified for cycling by the Consumer Product Safety Commission and the European Cycling Standard. Helmet Size Chart Measurement XS S / Youth M L / XL Circumference (inches) 18 7/8" - 20 1/8" 20 1/2" - 21 5/8" 22" - 23 1/8" 23 1/2" - 24 3/8" Circumference (centimeters) 48-51cm 51-55cm 55-59cm 59-62cm