They are paper wheels I mounted on a cheap grinder after removing the guards and guides and such. One is coated with diamond dust embedded in glue, to which you apply a wax before each use, the other is slotted radially along the circumference, about 1/2" in from the edge, to which you apply white rouge each time.
You dress up the edge using the diamond wheel, which is not terribly aggressive, but will put a new angle on a blade in two passes. That leaves a burr along the edge of a blade, which you then polish off with the rouge wheel. The end result is a polished edge that can be wickedly sharp and seems to hold longer than using any other sharpening method. I have a friend who's been using the same pair of wheels since 1989, and has only re-coated the diamond wheel once. Given the amount he needs to sharpen on a regular basis I'd say that is pretty good durability.
It takes me about 2 minutes tops to put a new edge on most pocket knives, and I have learned to make it beveled or convex (of sorts). It works for me. The alternative is using one of those carbide draw shapeners if I am out in the field and need to touch up an edge.
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The ultimate result of shielding men from the effects of folly is to fill the world with fools.
-- Herbert Spencer, English Philosopher (1820-1903)