Recommended for children age 3-5, but will fit most heads measuring 45-53 cm Always take a head measurement. Head sizes and shapes can vary, even within an age range. Using a helmet that doesn't fit can be dangerous. Easy to adjust chin strap Aerodynamic cooling vents Complies with the U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 1 and Older (Extended Head Coverage). Also complies with U.S. ASTM Safety Standard for multi-impact Skateboard Helmets. Shock absorbing inner shell