Double sided water stone. Coarse 250 grit for removing knicks and fine 1000 grit for finishing. Proper maintenance of a knife is very important. A sharp, well honed edge is essential for a clean cut. There are a number of ways to sharpen a knife, but water stones are the preferred method, because the user has absolute control during the sharpening process. Japanese whetstones in particular are said to produce a finer edge than North American stones due to the unique bonding process of the stone during the manufacturing process.