Peco Hex Bolt, Measurement System: Imperial, 3/8-16 Thread, 1 in Length Under Head, 5 Grade, Carbon Alloy Steel, Zinc Plated, USS Thread, 0.226 to 0.243 in H x 0.628 to 0.65 in W Head, Hex Head, 120000 psi Tensile Strength, Material Specification: ASME B18.2.1-1996, 1 in Minimum Thread Length, Rockwell C25 to C34 Hardness