[ Law of Motion]: For every action of the Cradle and balance balls pendulum there is an equal and opposite reaction, which inspires us to better understand the concept of conservation of momentum. The concept of 's cradle is very interesting, science physics gadget is great for science, and physics classes, [Looking for the Fun Physics Gadget]: Pull one or more balls, release pendulum, the same number of balls will swing on the other side, cradle balance balls not only looks great in the office but also an effective way to relieve the stress and frustration of office staff [Decompressive Balls]: The cradle is not only a toy but also a good tabletop decoration. You can put desk pendulum balls on your desk or shelf and shake it whenever you are passing by. There is a beautiful landscape in your home or office, physics balls pendulum make your home or office look more technological and modern [Novelty Desk Balance Balls Dcor]: This classic balance balls is made of high-quality materials. The metal ball and office desk decoration accessories is a reflective mirror surface, which is strong and durable, and can be stored for a long time. []: The pendulum balls and ball are suitable for adults and children, cradle balance pendulum is very suitable for learning science, killing boring time, and releasing stress, steel balance ball for kids is a good birthdays, Christmas or other size: 18 x 14 x 11CM Material: Plastic, carbon steel colour: silver Package Contents: 1 x ball ornaments Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.