Reduction gears are commonly used in transmission equipment requiring low speed and high torque. They achieve the purpose of reducing speed by meshing a gear with fewer teeth on the input shaft of the reducer with a larger gear on the output shaft. Standard reduction gears often have several pairs of gears with the same principle to achieve ideal speed reduction. The ratio of the number of teeth on the large and small gears is the transmission ratio.

The reducer plays a role in matching speeds and transmitting torque between the prime mover and the working machine or actuator, and is a relatively precise mechanical device. Its purpose is to reduce speed and increase torque. There are numerous types and models, each serving different applications. The types of reducers are diverse, which can be categorized into gear reducers, worm gear reducers, and planetary gear reducers according to the transmission type; into single-stage and multi-stage reducers according to the number of transmission stages; and into cylindrical gear reducers, bevel gear reducers, and bevel-cylindrical gear reducers according to the shape of the gears. Additionally, they can be further classified into spread-type, split-type, and coaxial reducers based on the arrangement of the transmission.