Product CE Kids Bike Helmet 50-58cm Ultra Light Children Cycling Helmet City Road Bicycle Kid Helmet For Outdoor Sports Riding Skating Scooter Specifications: Size (Approx.): S (50-54cm / 19.69-21.26in), M (54-58cm / 21.26-22.83in) Material: (shell) imported green PC material + (the main body) imported EPS foam Product Features: 1. It is compatible with for MTB and road bikes for kids. 2. It has passed CE/CPSC/SGS Certification. 3. It has passed the safety test. 4. The EPS foam was thickened. Advantages: It features good ventilation function with air holes and good protective performance, therefore it was specially designed for the endurance racing athlete kids. The inner EPS shock-release system was put in. We use the aramid filament to enhance the strength.