description of goods:This device demonstrates demonstrates conservation of momentum and energy via a series of swinging balls. Pull back one or more of the balance balls, release them and the same number of balls will swing up on the opposite side.Feature: Excellent educational science gadget. Not only demonstrates a pendulum, but also shows the laws of conservation of momentum and energy. Science toy. When feeling tired of studying and working, you can stir balls to hear the clinking sound to ease. Excellent educational & science gadget, own your very own piece of scientific history and explore significant values of physics. Pull back one or more of the balance balls, release them and the same number of balls will swing up on the opposite side. Great for home ornament, study or office desk table decor accessories, etc. Also good for birthday gift and kids toy. Specification: Condition: 100% brand newMaterial: Plastic + IronColor: Sliver Size: 18 x 11 x 14cm / 7.09 x 4.33 x 5.51 inch(appr.)Package Included:1 x Balance Balls ToyNote:1. Please allow 1-2 cm error due to manual measurement and make sure you do not mind before ordering.2. Please understand that colors may exist chromatic aberration as the different placement of pictures.