Designed to remove broken studs, bolts, socket screws and fittings, this Irwin 10-Piece Spiral Extractor & Drill Bit Combo Pack (11117) features an 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. The extractor size and recommended drill bit size are etched on each tool.