last fall i got my 3' bottle at praxair, i bought it, not rent. paid about 275$ for the full tank. i just went back to have it filled. i said i owned the thing. they exchanged it for a full bottle and it cost about 75$ i think. i didnt have to show them any paper work or anything. i think its 75/25 mig bottle. might be able to find it cheaper elsewhere.