1-3PCS Coupling Rigid Flange Plate Hardness Metal Coupling Guide Optical Shaft Aperture 2mm-14mm Size : 2mm.3mm , 3.17mm , 4mm , 5mm , 6mm , 6.35mm , 7mm , 8mm , 10mm , 11mm , 12mm , 14mm Material : Iron Surface treatment : Electroplate