Master Grade Premium sharpener is built not only by an engineer but an expert in the knife industry. This product is manufactured using the finest materials obtainable to ensure fine performance and lasting durability. Master Grade has exclusive patented angle guides that will sharpen the knife's edge up to 0.25" width and 0.08"high and create a perfect bevel knife blade. Most of knife sharpeners brands only sharpen blades up to 0.03" high, meaning that it will not be able to re-create a new angle when it's dull. Master Grade's unique angle guides prevent this problem. Endorsed by Chef Martin Yan as the one that works.