This is a Hello Kitty children's helmet. I bought it for bicycle practice, but it's a beautiful item that has only been used a few times. There are almost no scratches or stains. Measurements (approximate): Height: about 15 cm Diameter: about 20 cm Opening: about 15 cm - 17 cm The length of the straps is adjustable. The buckle functions well. It has been stored at home, so please understand and accept it as it is. Thank you.