EzyRoller works like this, using a locomotion principle called cambering motion. The simple left/right movement made by your legs pushing on the moving front bar creates an action/reaction similar to one used by snakes. There are no chains, no batteries just kid-generated power. The steel frame and polyurethane wheels ensure a solid and smooth ride on most surfaces (except grass and sand). Up to 70kg. Made of steel and plastic. Do not ride on sloped surfaces, near roads, cars, pools or when visibility is impaired. Always use protective equipment; always read safety instructions before use.