Description: Gravity At Work: See before your eyes as the Balls transfer fall and transfer weight across the gadget. Drop one ball or two balls. You can transfer in such an astounding way! Office Desk Decor: Show some character and express your love and physics with this decorating your office space. Can be meditative and fun to watch also! Educational & Classy: Experience the visual display of momentum. Use this in class and share with your friends and family the exciting world of physics and science! Quality Materials: 's Cradle is made of durable stainless steel, the metal balls are a reflective mirror Newtons Balls Edutainment: Suitable for children to experience the fun of mechanics in the process of playing this fun gadget also a perfect decoration for desks and tables, whether at the office or at home. Size Chart: S Size: 8.5cmx7cmx9cm/3.35inchx2.76inchx3.54inch M Size: 13.5cmx11.5cmx13.5cm/5.31inchx4.53inchx5.31inch L Size: 18cmx15cmx18cm/7.09inchx5.91inchx7.09inch Package Includes: 1 Newtons Cradle Balance Balls(4 Pack) Note: Please allow slightly errors due to manual measurement and different monitors.