PRODUCT SPECIFICATIONSPart #: 0000-114129Fastener Type: Square Head Machine BoltSize Description: 5/16"-18 x 1 1/4" (FT)Diameter/Nominal Size: 5/16"Length: 1 1/4"Wrench Size/Across Flats: 0.484-0.500"Width Across Corners: 0.665-0.707"Head Height: 0.186-0.220"Thread Pitch: 18Thread Pitch Type: CoarseThread Direction: RightThread Coverage: FullSystem of Measurement: InchGrade: A (2)Material: Low Carbon SteelFinish: Plain Finish (No Plating)Head Type: SquareDrive Type: External SquareStandards Met: A307Average Piece Weight: 0.0323000 lbs.Square head bolts, or square head machine bolts offer a large bearing area for positive gripping; primarily used nowadays for aesthetic projects that create a rustic look or to match existing fasteners; comes in both fully threaded and partially threaded pitches. Square head bolts are sometimes selected over hex heads because the head will fit neatly in a channel.