DiamondCore Rotary Tools have diamonds embedded all the way down to the shaft, not just on the outer edge. Ideal for cleaning/reaming out glaze drips in tight spaces or for bisque cleanup. Use them on bisque, high-fired clay, glaze drips, porcelain, tile or glass. For longevity use water, high speed and gentle pressure. "Let the Diamonds do the work." 2mm diameter x 15mm length. Shaft diameter 3.18mm. NOTE: This tool is not intended to be used as a drill. Use all appropriate safety precautions. Keep out of the reach of children.