Ninja Foodi NeverDull System Knife Sharpener keeps your Ninja knives sharp for over 10 years. 
It’s easy to use, just insert the knife and swipe the slider on the outside of the sharpener.  As you move the slider, the stone sharpening wheel applies pressure at the right angle to ensure a perfectly sharpened knife. The sharpener is slim and compact by design, making it easy to store anywhere. It’s a must-have for every kitchen.  I highly recommend!