A hand forged lamination of blue steel and wrought iron, tempered to Rockwell C64 degrees. "Blue Steel",� or "Aogami-Hagane"� is specially made by HITAACHI METAL CO., and is a more complex steel than "White Steel" or "Shiro-Gami" Japanese style hollow ground backs. Sizes in 24, 18, 12, 6, and 3 mm. These are by far the best chisels for the money and the ones I use.