50:1 Micro Metal Gear Motor
This gearmotor is a miniature (24 x 10 x 12mm), high-quality, low-current motor with 51.45:1 metal gearbox, similar to Sanyo’s popular 12 mm gearmotors.
These units have a 9.27mm long, 3mm diameter D shaped shaft.
These tiny, high-quality motors are intended for use at 6 V, though in general, these kinds of motors can run at voltages above and below this nominal voltage, so they should comfortably operate in the 3 – 9 V range (rotation can start at voltages as low as 0.5 V).
Lower voltages might not be practical, and higher voltages could start negatively affecting the life of the motor