Made from aluminium alloy material to reduce inertia Rigid coupling,high torque with rigidity,low inertia and excellent sensitivity No rotation gap, elastic action can make up for symmetrical angular misalignment Maintenance-free, oil proof and corrosion resistance Suitable for model car, model boat, hardware, mould, mechanical drive situations etc Specification: Size (DxL): Approx. 12x20mm/ 0.47x0.79inch; Color: Dark Red Size (DxL): Approx. 14x25mm/ 0.55x0.98inch; Color: Dark Blue/ Water Blue Size (DxL): Approx. 16x25mm/ 0.63x0.98inch; Color: Water Blue Screw Hole Diameter:4mm Transfer Pore Diameter:multiple specification Pore Diameter Tolerance:+0.02mm Model "5-6mm" means one end is 5mm pore diameter,the other is 6mm Size Chart: Model (Pore Diameter): 2-2mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 2-3mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 2-3.17mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 2-4mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 2.3-4mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 3-3mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 3-4mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 3-5mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 3.17-4mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 3.17-5mm, DxL: 12x20mm, Color: Dark Red Model (Pore Diameter): 4-4mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 4-6mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 4-7mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 4-8mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 5-5mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 5-6mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 5-6.35mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 5-7mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 5-8mm, DxL: 14x25mm, Color: Dark Blue Model (Pore Diameter): 6-6mm, DxL: 14x25mm, Color: Water Blue Model (Pore Diameter): 6-7mm, DxL: 14x25mm, Color: Water Blue Model (Pore Diameter): 6.35-6.35mm, DxL: 14x25mm, Color: Water Blue Model (Pore Diameter): 6.35-8mm, DxL: 14x25mm, Color: Water Blue Model (Pore Diameter): 6.35-10mm, DxL: 16x25mm, Color: Water Blue Model (Pore Diameter): 8-8mm, DxL: 14x25mm, Color: Water Blue Model (Pore Diameter): 8-10mm, DxL: 16x25mm, Color: Water Blue Package Includes: 1 piece Motor Coupling 1 piece Spanner 4 pieces Screws(7 Pack) Note: Please allow 1-3mm differs due to manual measurement Due to the different display and different light, the picture may not reflect the actual color of the item. Thanks for your understanding