Ron and All, My understanding of the #17.4 stamped on the container is that it is the "tare weight" - the weight of the empty container. You need to add that to the weight of the gas to come up with the filled weight of the cylinder. A full tank weighs 37.4 lbs. If you measure your gas tank and it contains 27.4 lbs, it is half full - 17.4 for the empty container plus 10 lbs. of propane. Regards, Randy Pickelmann MORNING STAR lying in Clearwater, FL www.morningstar.talkspot.com