Feature:1. Make the speed change smoother, the deep tooth guide wheel can effectively reduce the chain drop, the speed change is clearer, and the winding is more stable.2. Equipped with reducing sleeve, which is more compatible. The original aperture is 6mm, and the installation reducing sleeve can be converted to 4mm or 5mm.3. Made by CNC machining of 7075 high‑strength aluminum alloy and finely machined with a knife, with good wear resistance.4. Imported steel bearing, smoother, greatly reduced friction, higher strength, and improved riding experience.5. Goood bearing, flexible rotation. Suitable for 8/9/10/11 speed transmission system.Specification: Item Type: Bike Rear Guide WheelMaterial: Aluminum Alloy + Steel BearingProduct Size: Diameter: 50mm / 2inApplicable Transmission System: 4/5/6mm Screw Aperture; 8/9/10/11 Speed Transmission SystemPackage List:1 x Rear Derailleur1 x Guide Wheel Screw2 x Variable Diameter CasingNote:It is recommended to buy the same size as the original car.