Typical hardness on diameters 1/4 to 2 1/2 inches is HRC 33-39

1-14 x 2 Grade 8 Hex Cap Screw Yellow Zinc Plated

5/8-11 x 9 Grade 5 Hex Cap Screw Zinc Plated

Zinc plated material will meet or exceed ASTM F1941

1-8 x 7 Grade 8 Hex Cap Screw Yellow Zinc Plated

3/4-10 x 3 Hex Cap Screw SS 316 (A4) 5/8-11 A307 Grade A Carriage Bolts Zinc Plated Typical hardness on diameters 1/43 4 10 x 3 Hex Cap Screw SS 316 (A4) . 316 series stainless steel differs from 18 8 by its molybdenum content (2 3%) and a higher nickel content (10 14%). 316 stainless steel has greater corrosion resistance than 18 8 as well as superior strength at high temperatures.