M6 Hexagon Dome Nut - A4 Stainless Steel See Diagram for dimension key: d = 6 mm Thread Pitch - 1.0 mm m = 5 mm h = 12 mm s = 10 mm A4 grade stainless steel is also known as type 316 S31.This has a greater corrosion resistance than A2 in certain environments, and is often used for Marine applications especially when coming into direct contact with salt water DIN1587