Wind up the Fridge Rover’s gears + watch how it moves up the fridge’s surface, defying the force of gravity! Inside its clockwork mechanism, there is a coiled spring that winds up tightly as you turn the crank. This stores energy in the spring + when you let go, the spring uncoils, releasing the stored energy + turning the wheels. The wheels can grip the fridge’ s surface without falling because they’re magnets! An amazing science gadget. Measures approximately 1.75 x 2 inches.