The Double Sided Diafold Sharpener has two 4"x1" diamond whetstone surfaces - fine for a razor sharp edge and coarse to restore a neglected edge - in one lightweight, portable package that closes to 5 inches. DMT's monocrystalline diamond surface sharpens a wide variety of knives faster than conventional stones. Sharpen dry or with water, in the field or at home, no oil needed.