These are very good and very expensive whetstones.
If there is a negative side to DMT it is that they are too good (they will flat remove some steel so don't drink a bunch of Cokes or coffee before using one) and are they are expensive.
They come in various grits, course, medium, fine, and extra fine. They also sell them in different styles.
I would suggest that you check out the DMT website for details.
I had to fiddle around a bit to learn how to use them and hold a constant angle but am getting very good edges now in a short period of time.
They don't have anything like some sharpening systems that give you constant edge angles although you can buy a little angle guide from DMT that sets an angle. You put it under your blade when sharpening.
You don't use any oil or water with these, it is not required.
