Description This helmet features efficient ventilation to keep you cool while riding. It also features a built-in USB rechargeable integrated LED taillight to enhance nighttime and low-light riding security. Stay safe, stay seen. Features One-piece molding (EPS material), impact-resistant and drop-proof, effectively cushioning external impacts to the head, suitable for all types of riders. Specs Adjustable head circumference: 58-61 cm Dimensions: 29*21*13cm Weight: 240g How to measure my size? Helmet size is determined by head circumference. When measuring, use a measuring tape to wrap around the widest part of your head—from the most prominent part of your forehead (usually 1-2 fingers above your eyebrows) to the widest part of the back of your head. Take the maximum value after three measurements. Note The above product dimensions are measured manually and may have errors. They are for reference only. All accessories are non-refundable and non-exchangeable.