Atoplee 2 Pcs CNC Stepper Motor Shaft Coupler Flexible Coupling Motor Connector (6mm X 6mm) Industrial type D connectors in all silver colors Allows matching of couplers for dedicated hose applications. Length: 25mm Diameter: 19mm Material: Aluminium Shaft coupler Often used to connect servo motor, stepper motor, encoder, screw driving, machine platform, etc.