Kukko Bolt extractor set Super Traction" DescriptionChrome vanadium steel.Square for operation with a tap spanner and an open-end spanner. UseTo drill out worn bolts with right-hand thread, etc., in a set. AdvantageWide grooves for soft materials, e.g. brass, aluminum, VA, etc. How it worksBore out broken off bolts based on diameter.Screw in the bolt extractor.The sharp edges of the grooves get a good grip on the drilled in bolt and twist it out. Safety informationDo not use any electrical or pneumatic servo screwdrivers or hammer drills.Protective blanket required.Protective goggles required.