Naniwa Diamond Sharpening Stone | #400 GritNaniwa brand Diamond compound abrasive stone for knife sharpening. #400 for fast wear and new bevels Dimensions: 210mm x 75mm x 16mm. With Nagura stone for cleaning and abrading stone Naniwa diamond whetstones are incredibly hard, flat sharpening stones with diamond abrasives able to cut even the hardest modern blades. They are versatile, low maintenance, and have the ability to produce a mirror finish in minimal time. Each stone comes with a nagura