Carriage Bolt Inch Neck Type Square Basic Material Steel Material Grade Grade A Fastener Finish Zinc Plated Dia/Thread Size 5/16 In.-18 Fastener Length 2 1/4 in Fastener Thread Direction Right Hand Fastener Thread Type UNC (Coarse) ASME B18.5 Drill Size 21/64 in Head Dia 0.688 in Head Height 11/64 in Head Type Round Square Height 0.156 in Square Width 0.307 in Tensile Strength 74 000 psi For Use With Grade 2 Zinc Nuts Package Quantity 100