Kasumi knives are mode by forging together two types of carbon steels, Jigane & Hagane. Jigane is a softer carbon steel whose flexibility & ease of sharpening make it ideal for supporting the area around the blade edge. Hagane is a harder carbon steel which creates the sharp edge. Kasumi knives can be ordered either Aoko (Blue Carbon Steel) or Shiroko (white Carbon Steel). Available also in 6", 7", 7.5", 9" & 9.5".