Alan you may already know this but the tanks have pressure test expiration dates on them. Be careful if you buy one. If you buy one that is out of date or nearly out of date it will cost you about $100 to get it recertified. Gas companies also don't fill your tank anymore. They exchange them and will not exchange bottles from competitors. Renting eliminates these hassles but renting cost $10 per month from most gas companies. I've been down all these roads in the past 30 years. The best thing to do is go to your local welding/industrial gas place and do what they say. JMHO