Chrome Molybdenum screw and bolt extractors and Vanadium stud extractors. Screw type has left hand threads for removing recessed bolts/studs. Bolt type features reverse spiral flutes which bite down on rounded off bolts. Stud type includes 3 internal rollers clamping down and gripping stud allowing removal/installation. Contents: 3/8" Drive Bolt Extractor Set; 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm,19mm Screw Extractor Set; M14-M18, M11-M14, M8-M11, M6-M8, M3-M6 1/2" Drive Stud Extractor Set; 6mm, 8mm, 10mm, 12mm