DMT (Diamond Machining Technology) 11.5 Inch Dia-Sharp Diamond Bench Stone – Extra Coarse, D11XCrafted from the highest quality materials Built for performance and durability Made in United States Guaranteed not to hollow or groove, precisely engineered, assures consistent, even sharpening every time. Extra Coarse diamond to repair a damaged edge. Sharpens knives faster than conventional stones with DMT's monocrystalline diamond surface No oil is needed sharpen dry or with water Durable construction will provide years of consistent performance