This is a Bafang G040.500.DC hub motor. Buy it unlaced, or built into a complete wheel. 48V winding type, approximately 6.5 rpm/V. 36V winding (9 RPM/V) also available on request.
The unique feature of this hub motor is that it has a true 135mm OLD, meaning that it's a slip-fit into most bicycles' rear dropouts.
Doesn't require a torque arm on 98% of bikes.
8/9/10 Shimano/SRAM freehub body, 6 bolt rotor pattern. 9-pin HIGO male motor connector (6 pulse/rotation speed sensor).
Rated to 500 watts, capable of 1000 watts or more for shorter bursts.