4, Spiral Screw Extractor, Designed To Remove Broken Studs, Bolts, Socket Screws, Fittings, Aggressive Left Hand Spiral Design For Extra Gripping Power Spiral Flutes Are Designed To Embed Themselves Deeper Into The Metal As You Turn The Tool, So As The Fastener Resistance Increases, The Extractor’s Grip Increases, Removes Bolts, Screws 93238, 18 NPT, 18 BSP, 8 mm10 mm, Use 14 Drill Bit