Environmental protection and health. It is made of high-quality environmental protection and high-strength PP plastic. UV-resistant. Under the influence of high temperature, ultraviolet light and light, the activity of polymer molecules inside plastic increases, and the chance of contact with oxygen molecules increases, and it is easy to oxidize. UV has high energy, can destroy the chemical bond in the plastic, so that the plastic decomposes, we use a special formula to slow down the chemical reaction, avoid the product fading. Toughness and strength. Our product is not only hard in terms of firmness, we fully take into account that hard things will cause compound damage, so we ensure the strength of the product and provide full flexibility to avoid breakage and damage. Specification: Diameter 11 cm Material Plastic & Steel Function Stable metal supports Easy installation Individually adjustable Suitable for all bikes from 12 -20\" inches. Package includes: A pair of bicycle training wheels Note Make sure your child is safe when learning to ride a bike