The Newton*s Cradle is a classic desk toy. Also known as balance balls- the clacking of the steel balls will keep you entertained throughout the day. Pull back one or more of the balls- release them and the same number of balls will swing up on the opposite side. The balls will click back and forth until they stop after a few seconds. This miniature Newton*s Cradle is great fun for the office.***** Approximately 3.625* tall x 3.5* wide x 3* deep- balls are .375* diameter- plastic frame with chrome-like finish- black plastic base- easy assembly required.***** Please note- the balls do not swing indefinitely and eventually stop.****