This is the 2500 Grit Natural Chinese Sharpening Polishing Stone. This is a natural stone that can be used as a polishing stone for knives and swords. This is a natural stone  has a grit rating of approximately 2500 grit. As each of these stones are naturally formed, the grit rating on individual stones may differ and also depends on the amount of slurry formed and pressure used when sharpening and polishing. These stones need to be soaked, flattened and lapped before use. The stone comes in a wooden storage box.