The definition of the kids bike

Children's bike refers to a bike suitable for children aged 4-8 years, with a maximum saddle height of 435mm ~ 635mm, riding by virtue of the driving mechanism acting on the rear wheel. Various wheel diameters and styles with or without balance wheels. Children's bike cannot be used for road riding. 

If the size is too large, the child can't hold the handbrake tightly when braking, so he can't brake the car. So it's best to take your children to have a try when shopping(kids bike). In addition, the braking force shall not be less than 50N. Otherwise, the vehicle will not stop, causing harm to children. Some children's bicycles are also equipped with protective wheels (balance wheels), which can maintain the balance of cyclists. Therefore, pay attention to whether they are fully equipped (one on the left and one on the right). Do not dismantle them at will when using them. Parents must consider this when purchasing and using them