M4 Wing Nut - A4 Stainless Steel See Diagram for dimension key: d = 4 mm Thread Pitch - 0.7 mm D = 8 mm e = 17.6 mm h= 8.6 mm m = 2.9 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