Diamond File-Needle-Set of 5 170/220 Grit Fine Engineered to deliver performance unequaled by any other file, for use on ultra-hard materials. Carbide hardened steel, exotic metals, ceramics, and glass are no match for these precision files. Excellent material removal is the result of a unique process which bonds the 2-1/2" (64 mm) long diamond surface. Illustration is to show shape, all sides coated. 5-1/2 overall length. Used by Professionals