M20 Hex Nut - A4 Grade A4 grade stainless steel has a greater corrosion resistance than A2 in certain environments. It is often used for Marine applications especially when coming into direct contact with salt water Where: e = point to point m = thickness s = across flats d = Thread Thread Pitch - 2.5 mm e - 32.95 mm (min) m - 14.9 mm (min) s - 30 mm d - M20 DIN934