With a simple one-step adjustment system called True Fit, you simply tighten or loosen the chin buckle and are ready to ride. See owner's manual for instructions Recommended for ages 5+, but will fit most heads measuring 52-56 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 Complies with the U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 5 and Olde 9 vents to keep little heads cool PinchGuard helps ensure pinch-free buckling Disney Princess child bike helmet featuring beloved princesses like Moana, Ariel, and Mulan. Features like PinchGuard buckle and nine vents help keep heads ventilated while your little one cruises the neighborhood, park or trails. One-step adjustment system called True Fit, you simply tighten or loosen the chin buckle and are ready to ride.