Video industry uses them extensively
Mine is rated for 560lbs and collapses very nicely and has lasted 10 years.
Weighs 20 lbs and uses large tires
These are considered pro video equipment, and therefore not cheep (read as >$150).
You can find them at B and H photo: bhphoto.com
Expensive, but you will never need another.
H
Collapsible vs inflatable
I'm surprised that inflatable dollies haven't come up in this thread yet - maybe the level of discourse on the CDF is becoming more elevated. I'm doing my part to prevent that!
Mike