If you are anything like me (or most of our customers here at Hillco Fastener Warehouse), then measuring fittings can be very confusing. Heck, all fittings are confusing, if we're talking about the size designations and what they are called. For instance, we had a customer trying to complete the plumbing on an off-road project recently. He came into the fitting area with that glazed look in his eyes, so I could tell that I better drop everything and focus. Here's what he said: "I need a 3/8" fitting to come from the oil pump, but the other end to the pan is 1/2" or so. Also, the fuel pump is 3/8" male, which needs to go to the carb, which is A-N. And I need to install an oil temperature gauge, but it has to be male threads. And I would like to use stainless steel braided hoses if I can afford it. How much is this going to cost?" I quickly discovered that the glazed look in his eyes was contagious, because now I had it, too! So, the first thing I did is what I always do when someone comes in looking for brass or Fragola A-N fittings: I grabbed a pencil and a sheet of paper. I have found that, where fittings are concerned, a picture is worth a thousand words. Just basic diagrams work, so that the customer can point out where he needs a male or female fitting, for example. But where it really gets confusing is if the customer doesn't have a sample of the piece they need to replace. Why? Because, there are many different call-outs regarding thread designations. Bolts are easy. If it's American, and if it fits in the 1/2" hole in the gauge (note: if you don't have a Hillco bolt gauge {HI00001-$4.00}, get one! You will find that it will be one of the most-used tools in your tool box), then it's called a 1/2" bolt. Simple! But I have on my desk in front of me a 1/4" NPT pipe plug, a 1/4" A-N union, a 1/4" flare nut, and a 1/4" compression fitting. And guess what? They are all different, and none measures 1/4"! The pipe fitting measures 1/4" on the ID of the fitting, but about 1/2" on the OD. A compression fitting measures 1/4" on the OD of the tube , but the thread pitch of the fitting is 7/16-24. A flare fitting also measures the OD of the tube, but for a 1/4" flare fitting, the thread pitch is 1/2"-20. And, finally, the thread pitch on a 1/4" A'N fitting measures 7/16"-20. Go figure! So please, next time you're looking for a fitting, have some samples. And please, talk slowly!