Pololu - 78:1 Metal Gearmotor 20Dx43L mm 6V with Extended Motor Shaft

Pololu - 70:1 Metal Gearmotor 37Dx54L mm 12V (Helical Pinion)

Pololu 20D mm Metal Gearmotor Aluminum Bracket Pair 1138 - Eckstein S, 9,95 €

Pololu Aluminum Scooter Wheel Adapter for 4mm Shaft

Pololu Universal Aluminum Mounting Hub for 1/4 Shaft M3 Holes (2-Pac, 10,95 €

78:1 Metal Gearmotor 20Dx43L mm 12V CB w/ Extended Motor Shaft - RobotShop

Pololu NEMA 17 Stepper Motor Bipolar 200 Steps Rev 42×42x38mm 2.8V 1., 40,95 €

DC Spur Gear Motors - RobotShop

Pololu - Tillverkare

78:1 Metal Gearmotor 20Dx43L mm 12V CB w/ Extended Motor Shaft - RobotShop

Pololu Aluminum Scooter Wheel Adapter for 4mm Shaft

Motors - Optimus Digital

These small brushed DC gearmotors can deliver a lot of power for their size. This version has a 6V brushed DC motor combined with a 78.13:1 metal spur

78:1 Metal Gearmotor 20Dx43L mm 6V

Magnetic Encoder Pair Kit for 20D mm Metal Gearmotors, 20 CPR, 2.7-18V - Opencircuit