The Cutting Edge Rulers have a unique patented sharpening edge that will keep your rotary blade sharpened as you work! It is the same concept as a knife sharpener; each time you take a cut on the sharpening side you will run along the 650 grit diamond carbide edge. This keeps your rotary blade fine tuned and lasting longer. The fully frosted backing gives you just the right amount of steadiness for cutting, but also allows you to slide the ruler when you want to. The full frosting reduces visual clutter when you are looking for the numbers to use. The Cutting Edge 6 1/2" x 61/2" Square Ruler, with diamond powder edge.