Reduction gear mechanism directly connected to AC servo motor output shaft. Converts high-speed servo motor rotation to appropriate speed and torque for precise positioning and high-accuracy control. Available in planetary gear, harmonic drive, and parallel shaft configurations with reduction ratios from 3:1 to 1000:1. Used in NC machine tool feed axes, robot arm joints, automated assembly positioning mechanisms requiring high precision. Features low backlash and high rigidity, supplied separately from servo motor body.