RP#62, Mine are 10cuft acetylene and 20cuft oxygen I believe. Paying more than you are for the bigger bottles. They are exchange though. Nobody will fill the small bottles. They all say its not worth it unless they fill 100 at a time. Kind of pissed me off when i paid $300 for the setup with new bottles and couldn't get them filled anywhere within 50 miles
Mark, I use the disposable mapp bottles too for heating things. Oxy acetylene I mostly use for cutting. I live in Ohio with salt on the roads. A lot of suspension parts need cut off or heated cherry red to come off of these rusty old cars. None of my customers have nice new cars. If they did I wouldn't eat as well as I do.
Next time you go to exchange them see what the extra cost would be for larger bottles. May be cheaper in the long run. I only use O/A for heating/bending and once in a blue moon to cut. Any welding is done with TIG or stick. Last time I had the bottles filled (about a year ago) I found I could of gone up a size for a couple of bucks more.
-RP