During the grinding process, the abrasive grains in the grinding wheel ensure that the material of the workpiece is removed. The choice of grinding wheel grit (grain size and hardness) depends on the surface of the material to be processed and the application. The coarser the grit size, the more the material to be processed is removed. A grinding wheel with a coarse grit is therefore better suited for rough grinding. A finer grit is particularly suitable if a high surface quality of the material to be worked on is to be achieved, i.e. for fine grinding and polishing work. All abrasives are classified according to their grit size into the categories "coarse", "medium", "fine" or "very fine". The grit sizes range from P12 (coarse) to P5000 (very fine) for flexible abrasive products (grinding paper, abrasive belts, flap discs, coated abrasives) and F4 (coarse) to F2000 (very fine) for non-flexible abrasive products (grinding wheels, cut-off wheels). The smaller the number, the coarser the grain. The hardness of a grinding wheel is the resistance that the bond offers to the grinding wheel when the abrasive grain breaks out. The harder the material to be processed, the softer the bond should be. However, a very soft bond also leads to faster wear. The degree of hardness is indicated by A (extremely soft) to Z (extremely hard).