["Advantage: The shell of this kids helmet is made of hard and wearable PC material the interlayer material is lightweight EPS foam. These two materials provide excellent protection and cushioning in the event of an accidental impat" Safety: This helmet complies with U.S. Consumer Product Safety Commission Safety Standard for Bicycle Helmets for Persons Age 5 and Older Anti-Slip & Stable Design: The anti slip sponge increase the comfort of wearing. The strap adjustor provides more adjustability giving greater flexibility for a better fit. The retention system at the back of the helmet can be adjusted to fit the size of the head shape making the helmet more stable Appearance: The helmet has 14 ventswhich provide maximum ventilation for sports. The shape is more compact and lovely. The color is more fashionable and the frosted texture is more advanced Available in 2 sizes: XS: 48-50 cm (18.9-19.7 inches). S: 51-54 cm (20-21.26 inches)]