Tool steel extractors have a left hand helical flute designed for extra gripping power Drill bits are made of high speed steel for high hardness that could drill on most screws This set is designed to remove damaged or stripped screws, bolts, fasteners Easy to use, first drill a hole in the center of the broken screw with the appropriate drill bit, then use a suitable extractor to remove the screw Come with a tap handle which can firmly hold the extractor; for the large puller, you can use an adjustable wrench Product Description Specifications: Material: HHS (drill bits), tool steel (pullers ) Suitable screws (for reference only): #1 for M3~M3.5 #2 for M4~M4.5 #3 for M5~M7 #4 for M8~M9 #5 for M10~M12 Diameter of drill bits: 2.0mm , 3.0mm, 4.0mm, 6.5mm, 7.5mm Features: This set is designed to remove screws, bolts and fasteners that are damaged or naked. The drill bits are made of high speed steel for high hardness which could drill on most screws. Tool steel pullers have a left-hand spiral flute designed for extra gripping power. Easy to use, first drill a hole in the center of the broken screw with the appropriate drill bit, then use an appropriate extractor to remove the screw. Come with a tap handle which can firmly hold the extractor; for the large extractor, you can use an adjustable wrench. Package includes: 1 x set of broken screw extractor