This item is used as decorative ornament for home and office or friends or someone you love. The unique exclusive contemporary design makes it attactive and eye-catching. It can be applicable to desk and household decoration and also can be as a birthday gift. These swinging balls will keep you occupied for hours at work. When feeling tired of studying and working, you can stir balls to hear the clinking sound to ease. The bumper ball is a clever device that not only demonstrates a pendulum, but also shows the laws of conservation of momentum and energy. Features - - Material: ABS. - Size: About 18x15x17.5 cm. - Used as decorative ornament for home and office or friends or someone you love. - The unique exclusive contemporary design makes it attactive and eye-catching. - It can be applicable to desk and household decoration and also can be as a birthday gift. - These swinging balls will keep you occupied for hours at work and when feeling tired of studying and working, you can stir balls to hear the clinking sound to ease. - The bumper ball is a clever device that not only demonstrates a pendulum, but also shows the laws of conservation of momentum and energy. Package list: 1 x bumper ball without battery