With the introduction of high-carbon stainless steels, comes the need for a more aggressive sharpening surface than a conventional whetstone can provide. The DMT line of sharpeners incorporates a monocrystalline diamond face embedded in a nickel base for a lifetime of durable, dependable service. The blue DMT sharpeners are rated at 325 mesh, while the red is rated at 600 mesh. The Diafold Serrated sharpeners are specially shaped, enabling the Diafold to sharpen virtually any serration pattern. These diamond sharpeners are a must for anyone who wishes to sharpen a steel in the 60+ Rockwell hardness range.