The NMRV reducer is a modern type of speed reducer-also referred to as an RV reducer-and stands as one of the most common members of the worm gear reducer family.

Its fundamental operating principle is as follows: RV reducers are typically employed in transmission systems requiring low rotational speeds and high torque. They achieve speed reduction by utilizing a motor, internal combustion engine, or other high-speed power source to drive a small gear located on the reducer's input shaft; this small gear then meshes with a larger gear on the output shaft. The ratio of the number of teeth on the large gear to that on the small gear constitutes the transmission ratio.

Comprising a worm and a worm wheel, this mechanical transmission device features a compact structure, a high transmission ratio, and-under certain conditions-a self-locking capability. It is one of the most widely utilized types of speed reducers, distinguished by its minimal vibration, low noise levels, and low energy consumption.