This two-part aluminum assembly mounts directly to 6 mm diameter motor output shafts like those on our 37D mm gearmotors and allows you to drive most scooter, skateboard, inline skate, and other common wheels that are compatible with popular 608 ball bearings.

A two-piece aluminum adapter for transmitting wheel drive to motors with a 4mm diameter shaft. Mounting screws and set screws included. Pololu 2672

Tamiya 72008 4-Speed Worm Gearbox Kit

A small, low-power motor with a 5:1 metal gear, 6 V operating voltage, 0.02 A to 0.36 A power consumption, 2500 RPM speed and a maximum torque of 0.05 kg * cm. Pololu 1100

These 17 mm long aluminum adapters convert a 3 mm diameter shaft to a 12 mm hex shaft that compatible with many common hobby RC wheels. The set includes two adapters, two M4 screws for securing wheels to the adapters, four M3 set screws for securing the adapters to motor shafts, and one 1.5 mm Allen wrench for use with the set screws.

This gearmotor is a miniature medium-power, 6 V brushed DC motor with a 297.92:1 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. This version also has a 4.5 × 1 mm extended motor shaft.

Bipolar stepper motor. It has a resolution of 200 steps/revolution (1.8° per step), a rated voltage of 3.5 V, and draws a current of 1 A per coil. Pololu 2298

Copper alloy traveling nut intended for use with Tr8×8(P2) threaded rods and features a mounting flange with four holes threaded for M3 screws. Pololu 2688

A set of adapters (adapter) from the motor shaft 6 mm to 12 mm, wheel holders from RC models. Pololu 2687

Pololu Universal Aluminum Mounting Hub for 3mm Shaft Pair, 2-56 Holes

This compact, inexpensive plastic gearmotor (high-power brushed DC motor with a 120:1 reduction gearbox) is well suited for use in small robots. While intended for operation at 4.5 V, it should run comfortably in the 3 V to 6 V range.

This gearmotor is a miniature low-power, 6 V brushed DC motor with a 75.81:1 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. This version also has a 4.5 × 1 mm extended motor shaft.

Miniature high-power motor from the Pololu MP series. Gear motor 250: 1, shaft speed is 90 rpm, torque is 3 kg * cm (0.3 Nm). The motor has an extended shaft which makes it easy to attach the encoder. Pololu 2384

Motor with 25 mm diameter and 52 mm length, 47:1 metal gear, 12 V operating voltage, 0,3 A to 5,6 A power consumption, 210 RPM speed and 12 maximum torque. Pololu 3205

Motor with 37 mm diameter and 57 mm length, 131:1 metal gear, 12 V operating voltage, 0,2 A to 5,5 A power consumption, 76 RPM speed and 45 maximum torque. Pololu 4746

Motor with 25 mm diameter and 54 mm length, 75:1 metal gear, 12 V operating voltage, 0,3 A to 5,6 A power consumption, 130 RPM speed and 17 maximum torque. Pololu 3206

Motor with 37 mm diameter and 57 mm length, 150:1 metal gear, 12 V operating voltage, 0,2 A to 5,5 A power consumption, 67 RPM speed and 49 maximum torque. Pololu 2829

Motor with 37 mm diameter and 47 mm length, 12 V operating voltage, 0,2 A to 5,5 A power consumption, 10000 RPM speed, 0,5 maximum torque and 64 CPR encoder. Pololu 4750

Motor with 37 mm diameter and 68 mm length, 19:1 metal gear, 12 V operating voltage, 0,2 A to 5,5 A power consumption, 530 RPM speed, 8,5 maximum torque and 64 CPR encoder. Pololu 4751

Motor with 37 mm diameter and 50 mm length, 6,3:1 metal gear, 24 V operating voltage, 0,1 A to 3 A power consumption, 1600 RPM speed and 3,5 maximum torque. Pololu 4688