These are superfine grits, the stones are used to bring the metal to an absolute mirror finish, and hence an ultra sharp edge. Whereas the coarser stones can be stored in water, these fine stones are harder and not so porous, so only need to be sprinkled with water just before use, and left dry at all other times. They are mounted on bases and the very finest are supplied with a Nagura stone; used to de-glaze, true and build up slurry on the surface of the stone, which helps the polishing process. The 4,000 and 6,000 grit measure approximately 190mm x 63mm x 19mm and the 10,000 grit 200mm x 75mm x 25mm. The 10 thousand grit stone is supplied with a Nagura stone. As a guide a 6,000 grit is a good choice for everyday work.