1. Double and Larger Washer: The optimization has been tested with double hardened steel of the wheel, which is quiet and comes with an extended lifespan. Additionally, we have specially enlarged the washer to ensure it fully covers the assembly. Even after your child has ridden it, you won't need to worry about sudden drops or parts falling to the ground. Safe and worry. 2. Universal Diameter and Available Sizes Tired of products that only fit one or two bike models? No problem. With 5 different hole options, it meets your needs and can be mounted on bikes with sizes 12, 14, 16, 18, and 20 inches. The round and sleek design complements each other like a lollipop, giving your kids a vibrant visual appeal. (Note: For bikes with variable speed.) 3. Thickened Wheel with Quality PU Material We've pursued silent and durable bike wheels, especially those that also provide shock absorption. This wheel is made from PU material. The thicker wheel, with a 25 cm thickness (0.5 cm thicker than standard), reduces bumps and ensures effortless riding with less effort and more comfort.