These stones 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 10000 grit 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 wooden bases and 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.