The DC4 whetstone consist of a fine diamond stone (25 micron) and a very special ceramic stone, made of synthetic sapphires. The advantage of these materials, although they get worn, will still keep their flat shape this is important when you sharpen your knife. And, since these materials are the hardest we know of, they will sharpen any steel, even these extremely hard powder steels. You don't need any lubrication for these stones but now and then you should consider cleaning them with warm water and liquid soap. The stones might feel coarse from the start but will become smoother/better after some use. Size 4", leather pouch included.