Jam Nut, Nut Style Heavy Hex Jam Nut, System of Measurement Inch, Basic Material Alloy Steel, Material Grade Grade 2, Fastener Finish Black Oxide, Fastener Thread Direction Right Hand, Dia./Thread Size 5/16 In.-18, Fastener Thread Type UNC (Coarse), Width Across Flats 9/16 in, Nut Height 13/64 in