Medium: 53 - 48cm Rear adjustment wheel 11 vent system Strap adjustment Injection moulded ABS hard plastic Meets ASTM F 1447, CPSC, CE bicycle helmet standards The Red Goggle helmet by Kiddimoto brings style and safety together. Not only can you use this helmet on your Kiddimoto bike or scooter but you can use them for cycling and skating. The vents in the helmet keep you cool whilst the rear adjustment wheel provides a comfortable personal fit to your child's head. Top tip To measure your child's head use a measuring tape and measure around the widest point of the head which is about an inch above the eyebrows.