6-piece set. Designed to remove broken studs, bolt, and screws. Aggressive left hand spiral filters are designed to embed themselves deeper into the metal as you turn the tool, so as the fastener resistance increases, the extractors grip increases. Extractor size and recommended drill bit size are etched on each tool. High speed steel drill bit ensures, fast, clean drilling. Set includes spiral flute screw. Extractors in sizes: Ex-1, Ex-2, Ex-3, and HSS drill bits in sizes 5/64, 7/64, and 5/32.