Best Size：The PJ helmet is suitable for people with a head circumference of 22.04 to 24.00 inches. Adjustable straps and chin/neck pads provide the best fit. Note: This type of helmet is not suitable for people with a larger head circumference. The helmet is made of high-quality ABS engineering plastic+EPS anti-seismic foam plastic+Velcro+nylon. High quality foam is fully used inside the helmet, which is light and comfortable. The side rails are suitable for various accessories, and the integrated NVG bracket is compatible with most NVG style brackets. The colored bullet PJ quick helmet, Framework material: TPU super strong toughness, not easy to break, soft and lightweight. Lens material: polycarbonate, effectively wear-resistant and scratch resistant Lightweight design means wearing a helmet mask on your head will reduce fatigue while maintaining the same level of protection required for high-intensity outdoor activities. Very suitable for Airsoft, CS gaming, and other outdoor activities.