What is a Kids Bike?Bikes ranging in wheel sizes from 12 (normally for riders aged 3 to 5 years), up to 20 (normally for riders aged 6 to 9 years). The correct size would be determined by the height of the rider. Designed in girls and boys models and also in a number of styles. For more information on children’s bikes see our Children’s Bikes Buying Guide.Kids bike sizing guide