Its 2ft sq with a half ball 8ins deep, great for agilty balance and shadow boxing on your moving all the joints in the body at once We made the first one about 30 years ago,but kept it secret for years. THen Reebox started producing them 2 years ago, Iwondered if anybody had tried one.

http://www.youtube.com/watch?v=iBaA7tNSRNk