... as hard as diamonds. Features: 1.Special Materials: Using high-tech Zirconia crafted, high-density, high hardness, never wear, hardness (HRA87 ... better than metal knife; 2.Healthier: Lead-free, non-toxic, acid resistance, alkali resistance, never rust, health environmental protection; keep food ... so fast when using ceramic knife to cut it high tech and fashion 4pcs ceramic knife set