Feature:1. Made of highquality aluminum alloy material, it is durable and has long service life.2. Positive and negative gear guide wheels alternate between positive and negative gears, which makes the speed change smoother and faster, and at the same time reduces the chance of chain drop.3. The ceramic material reduces the resistance, improves the riding efficiency, and makes the rotation stronger.4. It has a colorful appearance, stable performance, high reliability and exquisite workmanship.5. Suitable for most rear derailleur and supports 7/8/9/10 speed. Fits for almost all 12T mountain bikes and suitable for the use of 4/5/6mm guide wheel screws.Specification:Item Type: Aluminum Alloy Bicycle Rear PulleyMaterial: Al7075 Aluminum Alloy + Ceramic BearingProduct Color: MulticolorsMounting Size: 4/5/6mm axisProduct Weight: Approx. 15g / 0.5ozFeatures: Suitable for most rear derailleur, support 7/8/9/10 speed. One thick gear and one thin gear are convenient to fill the gap of the chain, reduce the expansion of the chain to speed up the speed change, and reduce the chance of chain drop..Package List:1 x Rear Guide Wheel2 x Reducer Ring2 x Guide Wheel Cover