I have never seen those before. Those would be great! I can see a ton of excercises, in respect to throwing, possible.
You can get a whole set for 700 bucks, which isnt that much, my brother and are looking at going halves for them.

I think it will be great for winter, being indoors and still being able to chuck stuff around without wrecking the place.

They seem to be used by pro atheletes here, i.e. all blacks and super 14 players, and they are some strong fit lads.

Phil C