Virtual flywheel / sliding rod design of chain tension device / H-type chain groove structure / small volume design / magnetic storage Sliding design, using aluminum alloy sliding rod design, can slide left and right smoothly H-type chain groove structure avoids chain jumping when changing speed The flywheel inlaid magnet can be adsorbed on the iron tool wall. At the same time, there is a button placement slot, which can absorb a pair of buttons for standby (Products without buckle, need to match their own) Small size design, easy to carry when going out. It can be put into trouser pocket, tail bag and backpack. The chain can be fixed to avoid loose chain and scratch paint during transportation colour: blue+black Material: aluminum engineering plastic+stainless steel size: length 108mm Package Contents: 1*Bike chain Keeper Holder 1*Piston stop 1*steel wire Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.