1. Made of brass, antioxidant and durable 2. the side length is 7 mm, diagonal is 13.6 mm, height is 18 mm and the cylindrical outer diameter is 11.5 mm 3. coupler copper shaft coupling for DC motor car tire motor connection 4. hexagonal coupling is applied for connect the motor shaft and the hexagonal wheels, support for most of the motor shaft whose diameter is 7 mm 5. Suitable for coupler copper shaft coupling for the automotive tires, DC motor, robot and car Hexagon coupler size: inside diameter: 0.275 inch/7 mm Outer diameter: 0.452 inch/11.5 mm height: 0.708 inch/ 18 mm Hexagon width: 0.472 inch/12 mm Screw holes: size: 7mm Material: copper colour: gold Package Contents: 10 x shaft motor flexible coupling coupler 20 x Screws 2 x Hex Wrench Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.