Consists of a small block of tungsten with hundreds of diamonds embedded inside it. The block is brazed to a shank and fitted with a wooden handle. Total length 8 inches. Width of block 3/8 inch. As the first row of diamonds is worn away the second row comes into play and so on ensuring many decades of useful life. The array of small diamonds leaves a fine fresh surface of abrasive on the grinding wheel which in turn leaves a fine edge on your tools.