Yoshida works with one of the hardest stainless steel commerically available. ZDP-189, manufactured by Hitachi Metals is one of the highest quality stainless steels available on the market. A powdered steel, ZDP-189 can be hardened up to 66/67 HRC, harder than all other stainless steels. Few factories have learnt how to take advantage of these ultra hard steels, but nevertheless these knives will retain their cutting edge for an extremely long time before needing to be resharpened.
The ZDP-189 core is clad by a layer of Damascus steel which protects the ultra hard inner core. Very few factories have the proficiency to work with ZDP-189 and these knives are hard to come by. The damascus line is the premium collection from Yoshida Hamono, production time is typically a year and we are only able to come by a few pieces each year.