Size: S (head circumference 48-53 centimeters) Size: m (Head circumference 54-57 cm) L (Head circumference 58-61 centimeters) XL (Head circumference 61-64 cm) Bicycle helmet, mountain bike, road bike, bicycle helmet, USB charging light This helmet is equipped with illuminated headlights and rear warning lights to ensure nighttime safety. The lightweight helmet and portable USB charging provide a simple walk. Product features: USB charging High density EPS material Lightweight, comfortable, and soft. Comfortable chin protection Adjustable pressure head Multiple ventilation holes for ventilation. Night safety helmet tail light design Front headlight and rear warning light illumination Durable shock resistant and shockproof casing The helmet taillights have three flashing modes Product specifications: Name: Electric Scooter Helmet Materials: EPS, PC Colors: Black, White, Blue, and Pink oh Weight: 500g/1 pound already Battery material: Built in lithium polymer battery Battery configuration: 750mAh Usage time: about 7 hours (full load) Scope: Electric skateboards, bicycles, balance bikes, skiing, mountaineering, etc. Packing list: 1. Electric scooter helmet 1x USB charging cable