DMT WME 4-Inch Machinist Diamond Whetstone with 1-inch continuous diamond area Extra-Fine Superior diamond sharpening stones Legendary quality Made in the USA Versatile, portable sharpener for home or shop use Extra-Fine diamond to polish and refine an 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 and reliable service