This motor operates with any voltage from 3 V up to 18 V. The speed depends on the operating voltage. At 3 volts the speed is 120 RPM. Each additional volt increases the speed by 50 RPM. The exposed shaft is 4 mm in diameter and 10 mm long. The speed reduction mechanism in this motor is a planetary gear box. Overall length: 66.5 mm Diameter: 24 mm max Connection wires: 20 cm long Rated voltage: 5V - 18V Operating voltage: 3V - 18V Condition: Used Warranty: 90 days Other features: Contain strong magnets and can operate as an electric generator.