The anodized treatment makes it very rust resistant and oxidation resistant. And the deep tooth design allows it to have a tight fit with the chain.Good compatibility and high lubricity make it very reliable and efficient. Three different specifications allow you to choose the most suitable one according to your needs.Made of aluminum alloy, ceramic and metal, it is very durable to use.There are three specifications for you to choose from: 11T, 13T, 15T.It is suitable for bicycle, mountain bike, road bike, cycling and so on.Item Name: Bicycle Rear Shift Guide WheelMaterial: Metal,Ceramic,Aluminum AlloyStyle: Ceramic BearingFeatures: Anti-oxidation, Good Compatibility, AnodizingSize Details: 11T: Diameter: 3.4cm/1.34\\ (Approx.)13T: Diameter: 5.1cm/2.01\\ (Approx.)15T: Diameter: 6cm/2.36\\ (Approx.)Notes:Due to the light and screen setting difference, the item's color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement.Package Includes:1 x Bicycle Rear Shift Guide Wheel