Using the included DC motor, build your own 2 speed gear box. Clear case lets you see the gears move. Motor specs: Operates 1/2 to 3 volts, 100ma start-up / runs at 15ma no load. Strong torque - 300 RPM @ 1/2 volt. Great for gear drives. 2mm shaft dia. Size 1 1/4" dia x 1 1/4" long.