The Apex Model Edge Pro Key Benefits : Patented knife guide system will sharpen any size or shape blade ( up to 3.5" wide ), including serrated knives Simple system determines the best angle. Knives can be sharpened at exactly the same angle every time, making re-sharpening so fast you will never work with a dull blade again. Custom formulated water stones free you from messy, gummed - up oil stones. Long lasting and in expensive to replace. Easy to change with a simple twist of the knob. Removes far less metal than electric sharpeners or grinders, eliminating wavy edges, adding to the life and performance of your knives. Removes nicks and dings without distorting the knife edge. Creates no heat - will not damage the temper of your knives. Sets up in seconds on any smooth surface. No power required. Comes with convenient carrying case - very portable. Requires no maintenance other than routine cleaning. Patented Knife guide system does not clamp the blade, so you can sharpen any length or shape blade up to 3.5" wide. Adjustable sharpening angles, from 10 , 15, 18, 21, and 24 degrees. Water Stones are mounted on plates so they can be changed in seconds with a twist of the knob. Manufactured from the highest quality materials in Hood River, Oregon, US.