What do you call those big, clear bubbles that you roll down hills in?

You get strapped to the inside and pushed down hills and stuff as an outdoor sport/fun thing. What are they specifically called?What do you call those big, clear bubbles that you roll down hills in?
Its called ZorBing


Its like a big hamster ball for humans :]What do you call those big, clear bubbles that you roll down hills in?
Zorbing. You can do it wet with water inside with you and you roll about inside or you can do it dry where you are strapped in.
there is form of it called 'zorbing' i think water is involved.


big clear spheres that you roll in can also be called human hamster balls :p