Gold Tone 3mm Smart Car Wheels Chassis DC Gear Motor Hex Coupling Product Name : DC Geared Motor Hex Coupler;Material : Copper Color : Gold Tone;Total Size : 18 x 12mm/ 0.71" x 0.47"(L*Max.W) Fit Motor Shaft Diameter : 3mm/ 0.12";Hex Hole Diameter : 3.5mm / 0.14" Screw Fixed Hole Diameter : 2.8mm/ 0.11";Weight : 15g Package Content : 1 xDC Geared Motor Hex Coupler