M16 Hexagon Dome Nut - A4 Stainless Steel DIN1587 See Diagram for dimension key: d = 16 mm Thread Pitch - 2 mm m = 13 mm h = 28 mm s = 24 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