- Versatile Compatibility: This bicycle headset bottom bracket bearing set includes 7 sizes ranging from 21mm to 40-32mm. Designed to fit a wide range of bike models including mountain bikes, road bikes, and children's bicycles, it ensures compatibility with most standard bottom brackets available. - Durable Steel Construction: Crafted from high-quality steel, these bearings offer exceptional durability. With inner and outer diameters from 32mm to 40mm and steel ball diameters between 4mm and 8mm, they are engineered for long-lasting performance under various riding conditions. - Hassle-Free Installation: The set contains 2 bearings for straightforward replacement or upgrades. Simply remove your old bearings and insert the new ones effortlessly. This quick process enhances your bike’s functionality without the need for professional assistance. - Enhanced Performance: Experience smoother operation with precision-engineered steel balls that reduce friction, allowing for seamless movement in your bike's headset and bottom bracket. This improvement in performance translates to a more enjoyable and efficient riding experience. - Practical Applications: Whether you are upgrading your mountain bike for rough terrain, replacing worn-out parts on a road bike for smoother commutes, or maintaining a children's bicycle for safe rides, this bearing set provides the reliability and compatibility you need. Choose this bearing set to ensure your bike operates smoothly and efficiently, enhancing your riding experience while providing the durability necessary for various cycling adventures.