The hoberman large rainbow sphere is an expanding and contracting ball it cleverly combines mathematics and geometry to create a surprising motion that fascinates children and adults alike pull outwards and it will grow from 23 cm in diameter to a whopping 77 cm give it a slight push and it will contract back to its original size why not give these tricks a try flip down hold the closed sphere by one hub on top of your open palm flip the sphere over and watch it open then flip it back to