Finished Hex Nuts in 316 stainless steel are designed for use with stainless steel bolts or screws with a specified minimum tensile strength equal or less than the specified proof stress of the mating nut. 316 stainless steel differs from 18-8 by it's molybdenum content (2-3%) and a higher nickel content (10-14%). This gives 316 stainless steel a higher degree of corrosion resistance and superior strength at raised temperatures. Hardness of Rockwell B95 - C32 for diameters 1/4 through 5/8. Rockwell B80 - C32 for diameters of 3/4 through 1 inch. Proof load of 100,000 psi for diameters 1/4 through 5/8 and 85,000 psi for diameters 3/4 through 1 inch.Star Stainless Screw Co.