Description:Center the extractor bit in the screw head and turn counterclockwise to loosen. For broken off screw shafts or bolts then you will need to drill a hole in the center before using the extractor bit so that the extractor has something to grab on too. Screw Extractors Sizes: 3-6mm, 6-8mm, 8-11mm, 11-14mm, 14-18mm / 1/8-1/4 inch, 1/4-5/16 inch, 5/16-7/16 inch, 7/16-9/16 inch, and 9/16-3/4 inch.Designed to remove stubborn, rusted, stripped, screws or bolts or hole threads, even factory installed carriage type bolts with no slots to remove from. Plastic storage case included. Great hardware tool for home or construction use.