So I saw this device on one of Ray Mears videos on youtube and thought it looked good. Its a small stone (they make a three inch and a four inch version, I bought the four inch) with a thin diamond plate fixed to a thin synthetic stone. I don't have anything very dull around the place to try the diamond side on, but it seems to be on the finer side of coarse. The ceramic side on the other hand is on the coarser side of very fine. Completely sufficient to create a shaving sharp edge. It seems like a very decent pocket stone for field touch ups. I bought mine on Amazon.com for around $20.