Peco Hex Bolt, Measurement System: Imperial, 1/4-20 Thread, 1-1/2 in Length Under Head, 5 Grade, Carbon Alloy Steel, Zinc Plated, USS Thread, 0.15 to 0.163 in H x 0.488 to 0.505 in W Head, Hex Head, 120000 psi Tensile Strength, Material Specification: ASME B18.2.1-1996, 3/4 in Minimum Thread Length, Rockwell C25 to C34 Hardness