2373-POLOLU 1000:1 Micro Metal Gearmotor HP 6V with Extended Motor Shaft
This gearmotor is a miniature high-power, 6 V brushed DC motor with a 986.41:1 metal gearbox, making it a great choice for applications requiring fine control at very low speeds. It has a cross section of 10 × 12 mm, and the D-shaped gearbox output shaft is 9 mm long and 3 mm in diameter. This version also has a 4.5 × 1 mm extended motor shaft.
Key specs at 6 V: 32 RPM and 120 mA with no load, 125 oz-in (9 kg-cm) and 1.6 A at stall. (Note: stall torque and current specifications are theoretical values; stalling the motor will damage the gearbox.)