Features: As a tool for protecting bicycles chain, it protects chain and frame when rear wheel is removed for transport or cleaning. Allows the bike to shifts with wheel removed, and the derailleurs can moved. It keep the chain tensioned and away from paintwork. Used to stop your chain from getting tangles up during transportation or when cleaning your chain, avoids tangles. Easy to use: Simply remove the rear wheel off bike, Clamps the chain keeper or dummy hub on dropouts. This is important tool for cleaning the chain or diagnosing certain derailleurs problems. Specifications: Materials: Engineering Plastic Diameter: about 5.2cm/2.05inch Package Includes: 1set Bike Chain Keeper note: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.