1,made from Zirconium (94.4%min); 2,sharp blade for long time; 3,ISO 9001,LFBG,SGS Testing 4 ... to diamond Ceramic Knife – High Density ZirconiaModel: 3", 4", 5.5", 6.5", ceramic knife eriesBlade Material: zirconium dioxide (ZrO2; also ... surface. Never rusts and will not taint food with metallic taste.Factory Advantages: ISO Certificate, LFGB,SGS ... services to you. Thank you. 6.5 inch ceramic knifes