Kikuichi's new SEM or Semi-Stain line raises the bar on Japanese knives to a new level as they have increased the Rockwell on these amazing knives to around 61 (very hard) but the steel is still stainless. This gives the user the best of both worlds; a knife that can hold an edge but doesn't rust easily. This is a mono-steel blade meaning it made of one single piece of steel and is tougher than most Japanese knives.