The Chef'sChoice G436 Three-Stage Manual Sharpener is the ideal solution for improved cutting performance on 20-degree class knives. Using 100-percent diamonds, the hardest natural substance on earth, our patented abrasives sharpen faster and easier to create a sharp, longer lasting edge. Using ceramic rods, the final stage delivers a polished knife edge. Precision angle control ensures accurate sharpening throughout the entire blade length. This unit is designed to work with both straight edge and serrated knives.