4-Stone Deluxe Diamond Controlled-Angle Sharpening System The 4-Stone Deluxe Diamond Controlled-Angle Sharpening System ensures that your knife edge sharpens to the exact bevel you specify. Designed to give your blade a professional, razor sharp edge every time, regardless of your sharpening ability. Excellent for beginners and advanced users alike. The original and legendary Controlled-Angle System is the ultimate in Knife Sharpening technology. All Lansky Controlled-Angle Sharpening Systems allow users to select the sharpening angles that are best suited for their knife's intended use. The four sharpening angles and their uses are: 17? Angle - A severe angle recommended for razor blades, fillet knives or similar tools.