Shaft fitting accessories to connect two different shafts and make them rotate together to transmit torque. Applied for RC model car, RC model boat, 3D printers, snow blowers, grinders and other DIY projects Color: Silver Tone; Outer Dia.: 9mm/0.35inch; Inner Dia: 3.17mm x 3.17mm/0.12inch x0.12inch; Length: 23mm/ 0.91inch; Fastening Screws: M3*0.5 The universal joint is made of 45# steel and with electroplated finish, sturdy and durable. Features with large transmission torque, high efficiency, stable transmission, small gap impact When you installing it, firstly install the two halves of the coupling on the two connected shafts respectively, then align, move and adjust the shaft to the correct place In order to give full play to its function, please start the installation within the maximum allowable eccentricity range