16 (sixteen) High-speed steel. (HSS) drill bits available in these sizes: 33/64, 37/64, 41/64, 45/64, 17/32, 19/32, 21/32, 23/32, 35/64, 39/64, 43/64, 47/64, 9/16, 5/8, 11/16, 3/4. These can drill wood, fiberglass, polyvinyl chloride (PVC) and soft metals such as aluminum. Cobalt drill bits are extremely hard and dissipate heat quickly. They’re mostly used for boring in aluminum and tough metals such as stainless steel. They all appear to be unopened and wrapped in their original packages.