Ok, I made a call and this is what my fence man said. He uses Wheatland steel fence material wt 40 or 30 Also it's heavy duty gate post not fence post material I also checked a piece that was cut and I see no welding inside the tube. I still could be wrong ?????? Strength abt 80,000psi bending and lowest is 50,000 All made in the USA de Skip K3CC