10 pieces Spiral Extractor & Drill Bit Set in Metal Index is designed to remove broken studs, bolts, socket screws and fittings. Its aggressive left hand spiral design is used 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. Extractor size and recommended drill bit size are etched on each tool. Set includes: small metal index case, Spiral Flute Screw Extractors in sizes: EX-1, EX-2, EX-3, EX-4, EX-5 and Drill Bits in sizes: 5/64", 7/64", 5/32", 1/4", and 19/64".