998-POLOLU 50:1 Micro Metal Gearmotor HP 6V
This gearmotor is a miniature high-power, 6 V brushed DC motor with a 51.45:1 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 6Â V: 625Â RPM and 120Â mA with no load, 15Â oz-in (1.1Â kg-cm) and 1.6Â A at stall.