This beautiful "Newton's Cradle" showcases the gleam of metal. Lifting and releasing a ball on one side causes the balls to swing back and forth with a satisfying clicking sound, allowing you to enjoyably experience the concept of momentum conservation. No batteries are required, so you can play with it anytime. It also makes a great desktop object for your desk or study. It's recommended for a change of pace during work or study, stress relief, and as a gift for science enthusiasts. *Please be aware of the risk of accidental ingestion by small children.* The outer box has a slight dent (deformation), but the contents are not affected.