Please measure your head circumference before buying
Bike helmets for men/women is fully adjustable to fit the head circumference size (M) 20.86-22.44 inches, (L) 22.44-24 inches,
Size M: Suggest for youth age 12+ years old, and slim ladies.
Size L : Suggest for adult men and women.
This bicycle helmet of ours is certified by the US CPSC and ASTM.