Balance Balls are a classic desk toy. Also known as Newton*s Cradle- 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... a soothing experience you*ll enjoy. Balance Balls make a great desktop gift. ***** 4.5* wide x 5* tall x 5* deep- balls are .5* diameter- silver plastic arms- black plastic base- simple assembly required.**