This part consists of an internal gear ring and a matching gear or rotor. The inner ring and the housing are fixed together, and the oil entering from the inlet pushes the rotor around a central point to revolution. This slowly rotating rotor is driven by a spline shaft to output into a cycloid hydraulic motor. After the advent of this initial cycloid motor, another concept of the motor began to evolve after decades of evolution. The motor has a roller in the built-in gear ring, the motor with roller can provide higher starting and running torque, the rollers reduce the friction, thus increasing the efficiency, even at a very low speed, the output shaft can produce stable output. The motor is quickly reversed by changing the direction of the input/output flow and produces equal value torque in two directions. Each series of motors has a variety of displacement of the selection to meet the various speed and torque requirements.