That's Rigid Metal Conduit. Yes, I have searched but can't find it. What type of steel is Rigid Metal Conduit made from? I am particularly interested in the mechanical properties. This is for a non aviation use. I am looking for something, relatively inexpensive, to use for an antenna mast, maybe 30 feet tall. Probably two nested sizes. If I had the properties I could evaluate my options with FEA software. Wind loading would be the primary concern. With all the expertise on here, I figured someone may know.