They are very nearly the same size as standard steel or aluminum cylinders. Unlike the recalled "Lite" cylinders, these are filament wound, not glued together, and seem to be a quality product. They are a bit lighter, even than aluminum. For use on a boat they have the additional advantage that they are less likely to scratch anything when you wrestle them off the boat, into the dinghy, onto the bicycle to get them filled. In a camper seems like less advantage. You can see the propane inside, so no mistake about fill level.