This is the Ninja Foodi NeverDull Sharpener. It keeps your Ninja knives razor sharp for over 10 years. Comes with a 10 year guarantee:) I included the Ninja knife in the picture so you could see how it works. Super easy to operate! No batteries needed! Just place the knives inside & pull up & down on the handle 10 times. With its NeverDull stone wheel sharpens the blade at the perfect angle & applies pressure to restore the blade to superior sharpness. It’s safe & so easy to handle. Works great!