This is a traditional stone fixer, like those that are commonly used in Japan. This one is 100 grit, and can be used to flatten anything from coarse to fine stones. These stone fixers need a brief soak before use, and will eventually also need to be flattened (which can be done on a flat section of the sidewalk, using a diamond flattening plate, wet/dry sandpaper on a flat surface, etc.). Although I personally prefer diamond flattening plates, these stone fixers are much more economical, and we recommend them for those who are just getting started sharpening, or for those on a budget.