Description: u3010Quality Materialu3011: Crafted from steel, this product offers exceptional wear resistance and protection, making it ideal for daily use and outdoor conditions. It extends the lifespan of your child's bike, reducing the need for frequent replacements u3010Precision Anti Friction Designu3011: The 9 pieces set and ball bearing assembly are precisely engineered to minimize friction during axle rotation. This ensures smoother pedaling, efficient power transfer, and helps children easily master cycling skills u3010Easy Installation Experienceu3011: Designed with user friendliness in mind, the installation process is straightforward to follow. Parents can quickly complete the setup without needing specially tools or skills, saving both time and effort u3010Wide Compatibility for Modelsu3011: Highly versatile, this product is compatible for most 12 inch - 20 inch children's bicycles and some tricycles on the market. There's no need to worry about model compatibility issues when upgrading your child's bike performance u3010Stable Riding Assuranceu3011: The integrated design of the bowl set enhances axle stability in children's bikes, minimizing wobbling during rides and providing a safe and smooth cycling experience for kids Specification: Material: Steel Size Chart: Suitable for 12-20 inch Kids Bicycle Package Includes: 9pcsset Bottom Bracket Cups Note: Please allow slightly errors 1-2cm0.39-0.79inch differences due to manual measurement.