1. Head circumference compatible with helmets: 49cm-54cm for ages 3-8. Note: Please choose the child's head circumference.2. Helmet materials: ABS outer shell with high density EPS inner shell, thick soft sponge, comfortable and durable.3. Compatible sports: scooter, skateboard, bicycle, rollerblade and many other outdoor sports activities.4.Certification: CE and CPSC certification, all of our kids helmets have passed CE certification, high protection for the child's head. your children.5. Guarantee: We are committed to adopting the best quality materials to make our helmets, and the size of the helmet can be adjustable, usually it is suitable for children aged 3-8 years old.