camp stove

I am looking for the size of the small propane tanks that I see people mounting on bumpers and trailers. Not the small green disposables and not the regular 20 Lb'ers. Also...Approximately how long do they last just being use for cooking?

Ok, before I had an inkling that I was going to turn my rig into an overland vehicle (about a month ago or so) we had bought a Camp Chef, big gas grill. It a rather large 3 burner stove with a grill attachment. I know I can sell it for a loss and get a more compact one... but. I am in a full...