Diamond Pocket Knife Sharpening Stone from Smith's.

Smith's 4" Diamond Sharpening Stone-Fine offers the ultimate in sharpening technology. It features multiple layers of micron-sized moncrystalline diamonds bonded in nickel to a flat metal surface. The new 4˝ x 1˝ sized diamond sharpening stone is mounted on a plastic base and has a plastic lid to protect the stone when not in use. During use, the plastic lid can be inserted into the bottom of the stone base to extend the height of the base and make sharpening your knife safer. The user’s fingers grip lower on the base and remove any chance of cutting your fingers when pulling or pushing the knife’s cutting edge across the sharpening surface.

Interrupted surface speeds sharpening 750 grit diamond-coated surface
Cover doubles as base extension
Straight-line sharpening groove for hooks and pointed objects
Micro-Tool Sharpening Pad for tips of your knife blade and small cutting tools
Lightweight and compact Abrasives: Diamond - Fine (750)