High Quality: The Newton's Cradle is composed of a metal ball, a plastic bracket and a plastic base. Use nylon line of good material instead of cheap fishing line. With unique assembly design, the Newton's Cradle is more stable and durable. Longer Swing Time: Due to the resistance and friction of the air, the Newton's cradle balance ball will continue to move for 10-20 seconds. You have enough time to observe the physical performance of the Newton's Cradle Balance Balls movement. Wide Application: Suitable for children to learn and understand Newton's laws of motion while playing this interesting gadget. Meanwhile, it is also an excellent desktop toy for the office, a good tool to relax your mind while you feel tired at working. It is a perfect decoration, whether at the office or at home. Assembly Note: Firstly, gently open the package. Secondly, gently take out each component. Thirdly, align and install. Please be patient and careful during installation, as excessive force may cause entanglement! Great Gift: Suitable for adults and children, a good toy for learning science, passing boring time, and releasing stress. There is no doubt that this is a good gift for birthdays and holidays. Easy installation, funny and educational.