Drill glass, marble, masonry, rocks, concrete etc... Drill glass, marble, masonry, rocks, concrete- just about anything you want! Super duty diamond coating on nickel plated high speed steel will give you excellent results even in semi-precious stones. Fluteless design brings more diamonds in contact with your stock. Lasts longer and works better than twist designs. Numbered sizes: #36 (0.1065"), #50 (0.0700"), #54 (0.0550"), #56 (0.0465"), and #60 (0.0400") Note: use on a low speed with coolant (water/oil)