1Aluminium Alloy: The RC key hub shaft coupling is made of premium aluminum alloy material, durable, high strength, and more refined appearance. 2Function: This flange coupling connector is fixed on the motor shaft through the key lock slot, and the motor is fixed on the wheel hub for connecting the motor and the wheel. 3Size: The RC flange coupling connector is unique designed, with 1/2in inner diameter, 56.8mm outer diameter, and 12.7mm hole diameter. 4Strong: In addition to the beautiful appearance, aluminum alloys do not bend like plastics under pressure or at high ambient temperatures. 5Easy to Install: It is easy to install and disassemble, and the original parts or damaged parts can be replaced directly to obtain higher strength.