Adjustable Size - The kids bike helmet features an adjustable design and an adjustment knob on the back of the bike helmet to help adjust the head circumference. Adjustable size: 20.9-22.8 inches (53cm-58cm), head width: 16 cm / 6.3 inch, head length: 20cm/7.9inch.Comfortable and breathable - The cycling helmet features a special aerodynamic design and breathable foam, and 10 vents to reduce air resistance and reduce sweat.High protection and safety - The bicycle helmet is made of PVC + EPS, durable and hard shell, comfortable and padded, which can absorb the pressure caused by external impact and bring a very light riding experience to the head .Occasion - Bicycle helmets are the best choice for every child, suitable for cycling, skateboarding, roller skating, wrestling, cycling, roller skating, longboards and flying vehicles.Quality Assurance - For the safety of children, we dare not take it lightly. Made with qualified material, which is wear resistant and durable enough. If you have any questions about the products, please contact us any time.