You have to be careful though if you plan on using a fire extinguisher as a gas bottle, I have just been refused a fill by supagas because it is painted red not grey? or something, it would have been cheap though about $80 for 5 m3 of argoshield, I just took the bottle into the local tradezone store and they send it away to supagas. I got the people that check the extinguishers at work to fill it with co2 so not really a problem. This is for mig though, but just sharing my supagas experience.