Description This device demonstrates the conservation of momentum and energy through a series of pendulum balls. Pull back one or more balance balls and release them, the same number of balls will swing up on the other side. It can well develop kids learning skills and hand-on ability. Features - Color:As Shown. - Material:Plastic. Cotton Rope, Glass. - Size:14.50X7.20X13.80cm/5.70X2.83X5.42inch. - This Newton's cradle balance ball toy express your love for science and physics with this decorating your office space. - Pull one or more of the balls, release them and the same number of balls will swing on the other side. - When feeling tired of studying and working, you can stir balls to hear the clinking sound to ease. - Suit for both kids and adults, excellent for killing boring time and stress release. - Apply to psychology, teaching tools and furnishings. Frequency swing keeps you in a calm state.Package list: 1 set x kids toy