Now drill holes in glass with your Dremel rotary tool. This 1/4 In. (6.4 mm) diamond-impregnated core-style bit features superior long life and is ideal for drilling in both flat and contoured surfaces. The 360-degree diamond grit circumferences the bit allowing it to be used in a rasping motion to enlarge holes when needed. Holes on the side of the bit allow the removal of glass dust from inside the bit. For use on glass, ceramic wall tile, glass block, glass bottles, jewelry.