i did a little research on those and they don't exactly get rave reviews. The idea is that they allow the abdominus rectus to extend further thus allowing greater contraction. You can do the same thing with a Bosu which is a much better, more durable product.

The first ones just funny, the others informative.
http://www.youtube.com/watch?v=LFWuc-lmfeQ

http://www.youtube.com/watch?v=ylIpJ...eature=related