This fascinating anti-gravity demonstration works on the principle of repelling magnets and is ideal for discussing magnet levitation and frictional force experiments. With a simple twist of the fingers the axle and spins horizontally in a state of near perpetual motion for up to 20 minutes. Black and white reflecting strips on axle allow students to observe the patterns created by the alternating colors and to measure rotation speed using a stroboscope (not included). Approximate product size: 2-1/2" x 5" x 3" deep. Batteries are not required.