Product name: Protective helmetMaterial: PC shell, EPS linerProduct Highlights: Lighting Front Lights + Warning Tail Lights + USB ChargingHeadlight Mode: White light always onTail light mode: always on - fast flash - burst flashNumber of vent holes: 12Size: Adjustable knob on the back of the head, M: Head circumference: about 54-57cm, L: Head circumference: about 58-61cmBattery: 750mah power, 2.5h full charge, can last for more than 10h even in the most power-hungry mode 1Material: One-piece PC shell, effective impact resistance, wear resistance and drop resistance. Thickened EPS liner has the function of buffering and shock absorption. 2Lighting functions: Equipped with illuminated headlights + warning taillights, the headlights are in constant mode, and the taillights are adjusted in three gears, always on - fast flashing - burst flashing, making it safer to ride at night. 3Battery: 750mah power, 2.5h full charge, can last for more than 10h even in the most power-hungry mode.