Description:When you pull back one or more of the balance balls, then release them, the same number of balls will swing up on the opposite side,which demonstrates the principles of Conservation of Energy.With Newton's cradle design, it can be a classic creative toy that suits any desk space.Made of high quality metal, it is durable and sturdy.There are 3 sizes you can choose from:Small, Medium, Large.It is suitable for physics science, children teaching, room decoration, etc.Item Name: Newton PendulumMaterial:MetalSize:S: 11cmx9cmx9cm/4.33inx3.54inx3.54inM: 14cmx11cmx10.5cm/5.51inx4.33inx4.13inL: 17cmx13.3cmx13cm/6.69inx5.24inx5.12inNotes:Due to the light and screen setting difference, the item's color may be slightly different from the pictures.Please allow slight dimension difference due to different manual measurement.Package Includes:1 X Newton Pendulum