... ; 3,ISO 9001,LFBG,SGS Testing 4,hardness second to diamond Ceramic Knife – High Density ZirconiaModel: 3", 4", 5.5", 6.5 ... ", ceramic knife eriesBlade Material: zirconium dioxide (ZrO2; also known as zirconia)Blade ... hardness would close to the diamond, which ensures a longer lasting cutting than other traditional steel knife.Hygiene: no smell or oxidation ...