Haiku Kurouchi 6 3/4" Santoku the cutting performance will rise to an almost inaccessible level of sharpness. This is due to the unique design of the knife's blade: A sandwich construction that is made up of extremely hard, blue Aoko-steel at the center, which is then finished with protective layers of consecutively softer iron to ensure flexibility and stability. Please be sure to clean by hand and dry. Japanese blue steel is very high in carbon content and can rust. Be advised rust is not a warranty issue that will be covered.