Long story. My dad bought s set of the larger bottles years ago that you can only lease now.,He psssed away. The place he did business is closed. Bill of sale is gone. worked out a trade because I couldn’t get them filled or sell them. Now i’ve got the smaller bottles for sale that you can own. Bottles at nexair cost about $725 plus $130 to fill. $600 is a pretty good deal for someone that needs them. I don’t weld enough to need a backup set