This classic design is now available with SK-5 high carbon steel. It is the Japanese equivalent of American 1080, a high carbon steel with carbon between 0.75%-0.85% and 0.60%-0.90% manganese. As quenched, it has a hardness near Rc 65 and produces a mixture of carbon rich martensite with some small undissolved carbides. The excess carbide increases abrasion resistance and allows the steel to achieve an ideal balance of very good blade toughness with superior edge holding ability.