Three layers of diamond stones on each of the four sides nickel bonded to a steel frame.</br>No oil is required. Simply use a spray bottle of water during sharpening.</br>Four levels of coarseness: (600) Fine?? (400) Medium?? (300) Coarse?? (200) Extra Coarse</br>Shavings fall into openings on the surface of the sharpener to help maintain a cleaner su