3MM Shaft Motor Flexible Coupling Coupler for Wheel tyre DC Motor Robot*FD249 Product Description 3MM Shaft Motor Flexible Coupling Coupler for Wheel tyre DC Motor Robot NOTEThe screw for tightening isn't the identical every time,depends on the factory. Features Material: Brass Total length: 18mm Hexagonal edge to edge distance: 12mm Screw hole diameter: 4mm Package 3PCS X Coupling Coupler 6PCS X Screw 3PCS X Wrench