The Chef’s Choice 4643 AngleSelect professional manual sharpener is the ideal solution for both 15- and 20-degree class knives. Using 100 percent diamonds, the hardest natural substance on earth, our patented abrasives sharpen edges faster and easier. This sharpener improves cutting performance by creating two distinct facets set at different angles to form a sharp, longer-lasting, arch-shaped edge. The first stage sharpens 15-degree straight-edge knives, while the second stage sharpens 20-degree straight-edge knives. In the final stage, specialized diamond abrasives create a polished finish to both 15- and 20-degree knives. Precision angle control ensures accurate sharpening throughout the entire blade length. This unit is designed to work with both straight-edge and serrated knives. WHY YOU NEED A KNIFE SHARPENER – Over time, a knife’s edge dulls under the stress of cutting. The overall performance can be significantly improved if sharpened and maintained correctly. HOW DO KNIFE SHARPENERS WORK – Good sharpening systems shape the knife edge with a coarse abrasive and polish it with a finer abrasive. Covered by the Chef'sChoice One-Year Limited Warranty.