The extractors are made of an exotic tungsten alloy and the bits are solid cobalt alloy. In use by the professionals! This set includes LEFT HANDED BITS. When you use left-hand bit to drill the hole in a broken screw or bolt so you can extract it, the odds are good that the very act of drilling will remove the broken screw without ever needing to use the extractor. Your drill must be running in reverse when you use left-hand bits. A broken bolt or screw may be removed from a hole with a Screw Extractor. First, drill a hole in the broken bolt. The correct drill size to use is marked on the metal case. Insert Screw Extractor in the hole and, with a Tap Wrench, turn counterclockwise. The Screw Extractor acts like a corkscrew. It grips into the sides of the drilled hole and removes the broken part on its own threads without damaging the threaded hole.