Description Available in two sizes: Small (18.5-20.5 inches) and Medium (20.5-22 inches); Use a string and tape measure to measure your child’s head 14 air vents with integrated bug mesh in the front vents Extended visor for maximum protection, nylon straps, pinch guard chin strap Adjustable fit dial – turn right to tighten and left to loosen Complies with U.S. CPSC Safety Standard for Bicycle Helmets for Persons Age 1 and Older (Extended Head Coverage