700 grains/cm² to achieve a razor-sharp cutting edge on chisels, plane irons and other tools.Ensure tools have no dents or rough cutting surface, otherwise first treat with rough side of combination stone 528-COM.Dents and rough surfaces might damage the surface of this stone by making grooves.Homogeneous distribution of the quartz grains: constant and perfect use even after long use.Application: with water.Cleaning: leave stone to soak in water and vinegar for 12 hours