M12 spring washer A4 ss DIN 7980 A4 grade stainless steel is also known as type 316 S31 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 M12 – Outside diameter: 18 mm Material thickness:2.5 mm Object thickness (inc offset): 5-5.9 mm Material : T316 Stainless Steel (A4) Product Type : Washer Thread Size : M12