M12 Wing Nut - A4 Stainless Steel See Diagram for dimension key: d = 12 mm Thread Pitch - 1.75 mm D = 22.5 mm e = 49.4 mm h= 24.1 mm m = 9 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 DIN315