Bill & Candy Cycling MTB Road Bicycle Helmet 18 Holes Riding Equipment Male And Female Models,Suitable for people with head circumference 56-62cm and the head-width below 17.5cm Dial Fit adjustable system adds ease Ultra-light, wind tunnel, duct design, effectively reduce wind resistance. High-quality foam layer, the adjustment within the twist, you can adjust the size of head circumference. Suitable for people with head circumference 56-62cm and the head-width below 17.5cm. 18 flow vents to keep you cool with snap on/off visor for sun protection