M16 HALF NUT A4 SS (DIN 439) 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 Manufactured to the Din 439 standard M16 - Minimum thickness: 7.42 mm Across flats:24 mm Thread Pitch - 2.0 mm DIN439