These screws are manufactured with alloy steel, which contains elements to help the screws become more responsive to heat and mechanical treatments. Material / Carbon Steel Finish / Plain Thread Size / 16 Thread Direction / Right Hand Fastener Length / 3 1/2 in Head Width / 9/16 in Head Height / 15/64 in Tensile Strength / 125,000 psi Rockwell Hardness / C35 System of Measurement / Inch Thread Style / Partially Threaded Type / Medium Strength Thread Type / UNC (Coarse)