Features: This set is designed to remove damaged, rusted or stripped screws, bolts, fasteners. Tool steel extractors have left handed spiral flute designed for extra gripping power. There are total 5 extractors in various sizes for screws of diameter from 4mm to 18mm. Easy to use, drill a hole in the center of broken screw first, then use a proper extractor to take screw out. You may use an adjustable wrench to hold extractor firmly when removing screw. Specifications: Material: GCR15 tool steel Suitable Screws(Diameter): 1#: 4~6mm 2#: 6~8mm 3#: 8~11mm 4#: 11~14mm 5#: 14~18mm Package Includes: 5 x Extractors