Merkle-Korff PMDC Planetary gearboxes have the highest continuous and peak torque capability of any gearbox type. They also feature a very compact, low-weight design. The first stage planet gears are helical plastic for low noise. The pinion is hobbed directly on the motor shaft. The ring gear and secondary planet gears are sintered metal. The output shaft is hardened steel and is supported by dual ball bearings.