Professional Grade Motorcycle Helmet: Meets or exceeds DOT FMVSS 218 standard. Exciting fashionable design with lots of advanced features. Exactly what you need for Street Bike, ATV, Dirt Bike, BMX and much more. For both boys and girls. Outstanding Materials: Aerodynamic ABS Shell, Multi-Density EPS, Reinforced Chin Strap, Double D-Ring Buckle Ventilation System: Fully adjustable intake and exhaust vents to create a constant, light flow of air helping to keep the rider cool and comfortable. Comfortable Liner: Fully removeable and washable liner to keep helmet clean, fresh, and odor free. S (47-48 CM,18.5/18.9 Inch) M(49-50 CM,19.3/19.7 Inch) L(51-52 CM,20.1/20.5 Inch)