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