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 4", 5", 5.5", 7", 7.5", 8" & 9.5".