1Lightweight Design: The chain link is made of alloy structure, which is light but strong. Teeth are designed to avert the chain from falling off. 2Excellent Design: Integrated numerical control processing, stronger and safer, suitable for long-term cycles. Adding and subtracting tooth shape, the chain effect is better. 3Smooth and Beautiful: Bicycle chain links are made of high-quality materials, with smooth surfaces, bright colors, fading and corrosion resistance. It is easier to clean than traditional chain links and will make your bike more beautiful. 4Simple Installation: The versatility of the chain link averts the chain from dropping, and the installation is simple. 5Wide Application: It can be used for road bikes and folding bikes, support: 9/10/11 speed. Description: This Folding Bike Double Disc is made of alloy structure, which is light but strong. Teeth are designed to avert the chain from falling off. Specifications: Name: Folding Bike Double Disc Material: aluminum alloy Size: BCD: about 130mm/5.12 in Specification: 53-39 t Packing List: Folding Bike Double Disc*1