Dremel 663DR 1/4-Inch Glass Drilling Bit
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.