All Edge Craft pencil sharpener use 100% diamond sharpener, the hardest known material. This grinds any metal alloy faster, more efficiently and never ruins the temper of your edges. The diamonds keep the grinding surface cooler than other materials so as not to damage the blade, only sharpening. The manual cascading design of the 442 grinds the edge and then spares it into a razor-sharp polisher. This 4420300 has been specially developed for the wider geometry of tactical knives.