Hard Arkansas Wheel Unmounted, 2" diameter Natural, close-density oilstones with qualities that make them unequalled for sharpening tools such as gravers, knives, etc. These wheels come in 2 varieties: mounted or unmounted. Mounted wheels have a diameter of 3/4" (mandrel diameter of 3/32") and unmounted wheels have a diameter of 2". Both have a thickness of 1/4".