These robust modules boast a powerful high quality five pole motor with sintered bronze bearings & an integrated all-metal gearbox with bronze output bearings. The gearbox is epicyclic planetry which is smaller & more efficient than other types allowing the use of smaller motors & weighs less. The output shaft is cental & 6mm in diameter. Order RPM at Torque Code 4.5V6V9V12V15 Vgf.cm N02BQ70010001600215028002000N03BQ35507710313412000N04BQ68.514192512000