used to be so much easier before the metric crap. I ended up buying a set of metric Allen wrenches to carry on my work truck because most plumbing fixtures have metric set screws. It is really infuriating when you go to a "parts" store and they sell you the wrong item. I had the same experience as you Lash when I was running the brake lines for the Willys. I got to a point where I needed something like a 15" length to finish the front lines. I jumped in my car, ran to Auto Zone and got the line that was long enough to cut down. I get it cut, do the inverted flare, bend it to the right configuration, go to install it, and the fittings don't thread in, WTF!!! Yep, the idiot had sold me a metric line. I suppose some of it is on me for not checking it.I did notice that the tag on it was a different color but I didn't pay any attention to that, just thought it was the packaging.