Material: PC, EPSWeight: about 210gSize: all sizeHead circumference: about 57-63cm, head width: 18cm, head length: 22cmAdjustable: There is an adjuster knob to adjust the size of the head circumference.Suitable for scenes: riding, roller skating, skateboarding, etc. 11. High-quality materials: One-piece helmet, made of high-quality EPS cushioning foam and high-hardness PC material, reduces the bumps in the riding process, has strong impact resistance, and better protects your head. 22. Ventilation: Unique 18-hole ventilation design, effectively reducing wind resistance, dissipating heat, and keeping dry. The high-grade double-sided velvet lining strip prevents the growth of bacteria, suppresses the unpleasant smell of sweat, and does not stick to the hair. 33. Adjustable size: The bicycle helmet has a buckle that can be fastened. The rotating ring can be used to adjust the sealing of the helmet. There is a slider on the helmet adjustment strap that fits your head. The head circumference is about 57-63cm, suitable for most heads. 44. Widely applicable: Bicycle helmets are very suitable for everyone who rides bicycles, mountain bikes, roller skating, downhill, scooters and hoverboards. Designed for men and women, boys and girls.