The premise of all these knives is simple your blade is always razor sharp because when it gets dull, you toss it out and replace it with a new one. New blades cost about $1.60 – $2.00 each depending on the type. The blades are made with an inexpensive steel called 420 J2, which has poor long term edge retention but sharpens very easily and is extremely resistant to corrosion and rust. This steel, until these knives came out, had two primary uses.