Eze-Lap 3/16" diamond grinding stone with guide. For use with a cordless drill. Precision guide controls depth of cut and angle. Hook angle stays the same on each cutter. Sharpens chain in place on bar. Sharpens all teeth including carbide and HSS. No sparks, will not burn or temper the cutting edge. Gives twenty times the life of files and stones. Chains will cut longer between sharpening.