1、There is an adjustment knob on the back of the bike helmet to help adjust the heads circumference. 2、The helmet is made of thickened multi-density EPS foam material, which can effectively absorb impact energy and minimize the risk of injury to the heads during impact. 3、Helmets with brims can be protected from the sunshine, and reflective markers can be added to prevents collisions during nighttime rides. 4、The riding helmet is made of lightweight materials and is lined with breathable material for comfort. Using a professional aerodynamic and ventilation design, the air passes through the bike helmet to help increase speed and keep you cool. This product is made of fine quality environmental protections material and reinforced plastics sheet, with strong impact resistance, aging resistance, not easy to scratch. Features: There is an adjustment knob on the back of the bike helmet to help adjust the heads circumference. The helmet is made of thickened multi-density EPS foam material, which can effectively absorb impact energy and minimize the risk of injury to the heads during impact. Helmets with brims can be protected from the sunshine, and reflective markers can be added to prevents collisions during nighttime rides. The riding helmet is made of lightweight materials and is lined with breathable material for comfort. Using a professional aerodynamic and ventilation design, the air passes through the bike helmet to help increase speed and keep you cool. Specifications: Color: white, yellow, red, dark blue, blue+white, black+green, orange+white, black+white, red+black, pink+black, black (optional) Material: PC+EPS+PVC Heads circumference: 550-620mm / 22.05-24.41in Package size: 300 * 230 * 150mm / 11.8 * 9.1 * 5.9in Package weight: 196g / 6.9ounce Packing List: 1 * Helmet 1 * Helmet