Just to elaborate a bit on the response as to whether it was a recreational activity, I might have unwittingly misled you with my reply. The object is used as a recreational activity, in that you would utilise it in your spare time and for fun, but it would be unlikely to have a a long term usage, like a hobby, or a passtime, hence my answering with a no. Hope this helps...

[Raak] Round - yes, it is!

[Inkspot] Hollow - hmm, sometimes yes, sometimes no. I think, however, that in the traditional understanding of hollow, you would not say that it was, so once again I'd plump for overall no.