The original Hoberman Sphere--Rings. Expands from 9.5" to 30"!The Hoberman Sphere starts small and grows larger. And vice versa. Made of rainbow-colored plastic links, the sphere expands to 30 inches in diameter and contracts to a compact 9.5 inches. There's a hypnotic fascination in making the sphere expand and contract over and over again, but if kids want to do more with their sphere, a guide (included) lists some possibilities. How about trying the ballerina spin, the flip down, or the hot potato? The sphere can also be a fashion accessory. Think spiked hat or, even better, space helmet. Another option is to hang the sphere as a mobile. A pulley system is included, and a pull of the ring will cause the sphere to contract. Release the ring for expansion. Plenty of fun, the Hoberman Sphere might get kids thinking about mechanical engineering and some folding/unfolding projects of their own.