Details: *EASY TO USE: Simply remove the rear wheel off the bike. Clamp the chain keeper or dummy hub on the drop out. Keeps chain out of the way when transporting or wrenching on your bike. *DUAL FUNCTION: It is compatible with quick release drop out and 12mm thru axle. *CLEAN & TRANSPORTATION: YC-521 can be replaced freewheel for bike repair or chain clean Inserted into the right rear dropout when the wheel is removed for cleaning, storing, or transport. *COMPATIBILITY: Quick release lever allows for fast installation and removal. Works with all derailleurs and 1/8" chain, works on frames with 9mm open-type dropouts. *Material: Aluminum alloy, plastic *Color: Black (pictured) *Size: As shown *Suitable for all derailleurs and chains Package Contents:   1 * Chain holder