Peco Carriage Bolt, Measurement System: Imperial, 1/4-20 Thread, 1-1/2 in Length Under Head, Low Carbon Steel, Hot Dipped Galvanized/Zinc Plated, 0.563 to 0.594 in Diameter Head, 0.26 in W x 0.156 in D Neck, Square Neck, 60000 psi Tensile Strength, B70 to B100 Hardness, Material Specification: AISI 1006 - 1050/ASME B18.5.-1990, Round Head