Natural whetstone from the French Pyrenees.
It is composed of 2 grains:
-a medium grain useful for sharpening (to take up the edge of a dull knife)
-a fine grain useful for maintaining the edge (to take up the edge of a knife that is still cutting)
As these are natural stones, there is no defined grain size.
This stone does not require any particular maintenance. After a certain period of use and if necessary, you can clean the stone with a washing-up liquid, by brushing it under hot water.
Advice: see the page "maintain your Laguiole knife".