I know the original Hooverball was a leather 6 lb medicine ball. It looks like a bunch of people are using the Dynamax balls, even up to 20 lbs. I bought a 6 lb TKO ball, which was $30 locally. It has a rubberized outside and is about the size of a soccer/volley ball.
I threw this around to my workout partner and it seemed to work fine. I was wondering if it is worth buying a leather ball or stick with what I've got. Does anyone know the approximate size of the "regulation" hooverball?