Dremel 663DR 1/4 inch Glass and Tile Core Drill Bit with Cutting Oil. Now drill holes in glass with your Dremel rotary tool. This diamond-impregnated core-style bit features superior long life and is ideal for drilling in both flat and contoured surfaces. Diamond grit a full 360-degrees around the circumference of the bit allows it to be used in a rasping action to enlarge a hole if needed. Holes on the side of the bit allow the removal of glass dust from inside the bit. Each bit is packaged with Dremel cutting oil to increase the speed of cut and prevent damage to the bit from overheating. For use on glass, ceramic wall tile, glass block, glass bottles, jewelry.