Flexibility of coupling shaft removes stress between the motor and driving components. The shaft couplers are widely applied to small CNC machines encoding and 3D printers Z shaft coupling, simplifies the debugging difficulty. 6mm to 8mm shaft usage diameter, 25mm length, 18mm diameter, set screw type, beam coupling.Zero backlash. One-piece metallic spring coupling. For little torque shaft connect.Absorption of parallel, angular misalignments and shaft end-play by spring action.Widely used in drive systems for encoders, instrumentation,lead screws, small pumps, feed rollers and anywhere light to medium duty, torsionally flexible coupling is required. Material: Aluminum alloy Color: Silver Weight: 84g Package Content: 6 x Shaft coupling 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.