5/16"-18 x 2-1/2" Grade 8 Yellow Zinc Finish Hex Cap Screw / FASTENER LENGTH: 2.500 INCHES NOMINAL HEAD STYLE: C1 HEXAGON NOMINAL THREAD DIAMETER: 0.312 INCHES THREAD QUANTITY PER INCH: 18 MATERIAL: STEEL OVERALL MATERIAL DOCUMENT AND CLASSIFICATION: GRADE8 ASSN STD SINGLE MATERIAL RESPONSE OVERALL THREAD SERIES DESIGNATOR: UNC