M8 Hexagon Dome Nut - A4 Stainless Steel See Diagram for dimension key: d = 8 mm Thread Pitch - 1.25 mm m = 6.5 mm h = 15 mm s = 13 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