One two-sided Combination Ceramic stone Course (400) and Medium (1000) Grit textures Non-slip, durable plastic protective box Breathing holes to keep product safe and aid drying Ceramic is longer-lasting, more effective and much cleaner than conventional Corundum whetstones. These stones are much harder than the traditional whetstones, so they wear a lot slower. They will sharpen knives faster and are particularly good for a lot of the ultra hard Japanese steels, SG-2, HDP-40 and ZDP-189. The stones require a lot less lubricate, i.e. they just need a little water or oil and make a lot less mess as less material is removed.