5/16"-18 x 3-1/2" ASTM F835 Hex Drive Black Oxide Finish Alloy Steel Button Socket Cap Screw / THREAD LENGTH: 3.500 INCHES NOMINAL HEAD STYLE: C36 ROOF INTERNAL DRIVE STYLE: D5 HEXAGON END ITEM IDENTIFICATION: 2320-01-531-2701;TRUCK,UTILITY-INTERNALLY TRANSPORTABLE NOMINAL THREAD DIAMETER: 0.312 INCHES THREAD QUANTITY PER INCH: 18 PART NAME ASSIGNED BY CONTROLLING AGENCY: SCREW,BUTTON HEAD,SOCKET CAP SPECIAL FEATURES: MATERIAL: ALLOY STEEL THREAD SERIES DESIGNATOR: UNC