High-quality straight flute screw extractors For removing broken screws, bolts, and studs as well as pipe and fittings Tough carbon tool steel for long life High-quality, heat treated tool steel Drill size stamped on shank Surface-treated to resist rust Straight flutes provide maximum bite No binding or chewing of material Screw extractor# 1 U.S.S. screw, stud or bolt size 1/4", 5/16" Drill size 1/8" Minimum depth of hole 3/8"