Our gas tanks are all brand new aluminum tanks in standard sizing with high quality valves. Aluminum tanks are superior to steel because they do not rust. All tanks are shipped empty. To have tanks filled you will want to visit your local welding supply shop. Because most welding supply shops will exchange you a full tank for your empty tank (the majority do not fill on site) beware of purchasing off size tanks, such as 2.5 and 4 lb. 5lb and 20lb tanks are industry standard. Also be warned that you will want to make sure that you are getting high quality valves if you are buying reconditioned steel tanks that come from overseas. Tanks can be stored inside or outside of a refrigerator.,Fill with beer gas mix (70% Nitrogen/30% CO2) for dispensing beers "On Nitrogen."