1100-POLOLU 5:1 Micro Metal Gearmotor LP 6V
This gearmotor is a miniature low-power, 6 V brushed DC motor with a 4.995:1 metal gearbox. 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.
Key specs at 6 V: 2500 RPM and 40 mA with no load, 1 oz-in (0.1 kg-cm) and 0.36 A at stall.