Feature:1. Supporting for various speed shifting. Offers you a better cycling experience.2. Can be applied for most mountain bike, bicycles, road bikes, folding bikes, etc.3. Adopting aluminum alloy and ceramic material, this product is very durable to use.4. This ceramic rear dial guide wheel is strong and light. Ceramic bearings ensure durability.5. Easy to install, there are 2pcs installation accessories which help you install easily.Specification:Item Type: Rear Guide RollerMaterial: Aluminum Alloy and CeramicColor: As shown in the pictureSpecification: 15TLength Size: Approx.55mm or 2.17inInstallation Size: Approx.6mm or 0.24in axesSmall Ring Size: Approx.4mm or 0.16inLarge Ring Size: Approx.5mm or 0.20in.Package List:1 x Rear Guide Roller2 x AccessoriesNote:1. Please allow 1and 8209 2mm error due to manual measurement. Thanks for your understanding.2. Monitors are not calibrated same, item color displayed in photos may be showing slightly different from the real object. Please take the real one as standard.