Every action has an equal but opposite reaction - right before your very eyes with this fascinating Newton's Cradle Balance Balls Set. Science is demonstrated clearly and simply with a touch of amusement with this balance balls set featuring five metal balls suspended by invisible wire in a metal frame. Lift a ball, let it go and watch the ball on the opposite end move. Great for desks or home display. Measures approximately 4.5" x 4.25". Comes packaged in an individual box.