Natural premium novaculite quarried in Arkansas delivers the sharpest possible edge with a near mirror finish Hard Arkansas has an ultra fine grit that produces the finest edge possible while maintaining tolerances unequalled by any other abrasive file Applications include dimensioning keyways to maintain fit, stoning faces on router bits, touching-up edges of reamer teeth, lapping/honing to close tolerances to produce the finest edge on precision instruments, die work and delicate tools Comes in three convenient sizes: 3 x 1/4 inch, 3 x 3/8 inch, and 3 x 1/2 inch