Completely handmade by mr. Tsukahara. A core of the ultra modern Hap 40 metallurgic steel. Two outside layers of stainless steel. The core is semi stainless. This means that the Hap40 contains around 9% chroom. Stainless steel contains 12-14% chroom. So in normal use, clean and rinse with warm water and dry with a dry towel and then store your knife. This Hap40 steel is very refined and will be best maintaining it sharpenss with a whetstone.