I've also got a D4E "Diamond Sharpening Stone" in a couple of different grits for sharpening pocket knives. These are 4" long and 1/4" thick x 7/8" wide. They are pretty handy to have around and come in coarse, fine and extra fine. They call it a 'stone' but it is a piece of steel with the plating and the embedded diamonds like their larger plates we know and love.