Smith's new 4 inch diamond sharpening stone (item 50363) features Smith?s patented interrupted diamond surface which speeds the sharpening process by collecting and holding the metal filings removed from the knife or tool edge during sharpening. This keeps the sharpening surface clean and working effectively. The 4 inch diamond sharpening stone also comes with a micro-tool sharpening pad for sharpening the tips of your knife blade and small tools, a straight-line sharpening groove for fishhooks and pointed objects, and a stone cover that doubles as a base when not covering the stone. It is excellent for sharpening even the hardest steel blades and works best on small to medium hunting knives, tactical knives and everyday pocket knives.