These cylindrical brushed DC gearmotors are available in a wide range of gear ratios and 12V with long-life carbon brushes (CB).
All geramotors have the same 20 mm diameter body and 4 mm diameter gearbox output shaft, so it is generally easy to swap one version for another if your design requirements change (though the length of the gearbox tends to increase with the gear ratio).
Higher voltages could start negatively affecting the life of the motor, and lower voltages might not be practical. Four different gear ratios are available with us.
Specifications