We have supplied these custom grade 5 hex cap screws to our customer for well over 10 years.  The parts are manufactured domestically, with production runs typically covering 50,000 pieces at a time.  The shoulder is critical on these parts, set at .312" in diameter +/- .005" and at 1/4" in length.  Head dimensions slightly off the standard for this size and the finish is black oxide and light oil.  Together with a number of other parts we supply these custom hex cap screws through revolving annual blanket purchase orders that split up the annual usage to match our customer's seasonality.