The Hoberman Sphere is an expanding and contracting ball. It cleverly combines mathematics and geometry to create a surprising motion that fascinates children and adults alike. Its basic structure consists of six large intersecting rings. Each ring is made up of lots of small plastic links joined together in pairs which fold and unfold in a scissor-like motion. Give it a slight push and it will contract back to its original size. This patented method of folding was discovered by Chuck Hoberman- an inventor with degrees in art and mechanical engineering. The Hoberman Original Sphere comes with a pulley- hardware and instructions to hang it as a kinetic mobile. It also contains an educational booklet about the geometry of the Sphere and an activity sheet detailing 21 fun tricks and activities you can do with it.****Features:*** Unfolds from 9.5* to 30**** Ages 4 and up **