1. High quality materials: lightweight one-piece bike helmet made of high hardness EPS and PC materials, high density, durable and comfortable, compact shape combined with moulded polycarbonate shell, no smell and toxic substances, adjustable buckle closure, sturdy and durable, does not irritate the skin.2. ADJUSTABLE TO DIFFERENT HEAD SIZE: Adjustable belt and internal adjuster can adjust the size of the head circumference. Please be sure when riding a bike helmet. Wearing a helmet properly is very important for wearing a helmet, as helmets of all sizes are vulnerable to potential hazards. Please measure the head circumference correctly before buying. (Suitable for 57 - 62 cm head circumference).3. Extra protection: with fully adjustable belt and high-quality buckle, shock-absorbing inside, provides additional protection, can produce superior air circulation in the head, discreet innovative design. All this is equipped with a helmet and has everything your biker needs.4. Suitable for most people: It has 18 ventilation holes to reduce air resistance, keep you cool, comfortable and breathable, with removable, protective sweat-absorbing lining pads, comfortable to wear and easy to clean. Ideal for city cycling, technical climbing and all activities in between.