It's a tungsten carbide sharpener, just like the Sterling Sharpener, or Smith's, or....
Most folks here on Blade Forums don't like them (tc sharpeners)...
reasons why:
They remove to much metal
They are at a fixed angle, your knife might not be at that angle
If there's a nick in the edge, the carbide sharpener can end up making it bigger
For a knife that is extremely dull but not damaged, it'll make it cut again. It doesn't put a refined edge on it.
Smith's two stage sharpener (tc and ceramic) and their Pocket Pal (tc, ceramic, and a tapered diamond for serations) both have ceramic which can be used when the knife is a little dull and not extremely, avoiding the use of the tungsten carbide section.
If you are about to be a knife nut, you'll end up owning something like it, but you'll probably learn to sharpen free hand.
For $23, I'd spend an extra 20 and get a Spyderco Sharpmaker, unless you are looking to use this 'in the field'. For $13, you can get the same thing, only all metal and smaller... Sterling Sharpener.