A combined motor and gearbox unit,especially designed for educational use. The motor operates between 1.5 and 6V DC, and the unit includes interchangeable gears, giving a range of speeds and motor torques. * The clear polycarbonate housing provides mounting for both the motor and gears, and full instructions for calculating gear ratios etc. are included. * Shaft 4mm dia. x 24mm long (front). * 54mm long (rear).