Kutook Bike Helmet Road Mountain Cycling Helmet Adults (23"-24"; 58-62cm) Foam In-Mold polycarbonate shell with EPS Liner;safety, durable,shakeproof and comfortable Fits head circumference: 23"-24" (58-62cm), head width: 6.7" (17cm); compliable with adult size Integrated flow vents to keep rider cool,and reduce the wind resistance Suitable for cycling on the road and mountain