M12 Thin type nylon insert lock nut. A4 grade stainless steel Nyloc Type d = 21.1 mm h = 12 mm m = 8 mm s = 19 mm thread pitch = 1.75 mm Nylon insert can be various colours. Please ask if colour is important to you 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 DIN985