Hex Head Bolt ,Gr5, 5/16-18 x 1", Zinc. Used in various applications including manfold brackets and flanges, torque plates, and transmissions. Harley-Davidson part numbers 3987 and 4017. Note: All reference to H-D part numbers is for identification purposes only. We in no way are implying that any of S&S Cycle's products are original equipment parts or that they are equivalent to the corresponding H-D part number shown. S&S Part #: 50-0108