Mine came with diamond stones as well as hard Arkansas stones. I think the Arkansas stones do a better job on a finer edge, but i have only 2. Maybe i should invest in a new set and see if results change.I've used one for years....works well for me.
It's all about the angle.
The small notch is for very small blades. Bigger blades can go all the way in.I’ve had one for several years. It does a good job for me, but my biggest gripe is the small notch on the clamp. It’s hard to get it locked down and if the spine is radiuses at all, it really doesn’t want to grab. With only a small round knob to tighten down, you really have to bear down on it.