Peco Carriage Bolt, Measurement System: Imperial, 3/8-16 Thread, 3 in Length Under Head, Low Carbon Steel, Hot Dipped Galvanized/Zinc Plated, 0.782 to 0.844 in Diameter Head, 0.388 in W x 0.219 in D Neck, Square Neck, 60000 psi Tensile Strength, B70 to B100 Hardness, Material Specification: AISI 1006 - 1050/ASME B18.5.-1990, Round Head