Carriage Bolt Square Neck Round Head Low Carbon Steel Heat Dipped Galvanized Size 5/16-18 Length 3 In Head Diameter 0.688 In Head Height 0.156 In Square Width 0.307 In Square Height 0.156 In Drill Size 21/64 In Tensile Strength 60 000 For Use With Grade A Galvanized Nuts Grade A Package 100