PRODUCT SPECIFICATIONSPart #: 0000-120004Fastener Type: Hex Cap Screw (Bolt) - USASize Description: 5/16"-18 x 4 1/2" (PT)Diameter/Nominal Size: 5/16"Length: 4 1/2"Wrench Size/Across Flats: 1/2" (0.489-0.500")Width Across Corners: 0.557-0.577"Head Height: 0.195-0.211"Thread Pitch: 18Thread Pitch Type: CoarseThread Direction: RightThread Coverage: PartialSystem of Measurement: InchGrade: 5Material: Medium Carbon SteelFinish: Zinc PlatedHead Type: HexDrive Type: External HexAverage Piece Weight: 0.1037000 lbs.Country of Manufacture: United StatesHex Cap Screws, are similar to hex bolts, but are manufactured with tighter tolerances than hex bolts for socket or wrench tightening, hex cap screws are available in both fully threaded and partial threaded varieties, and in many different materials.