When you are faced with a rounded-off, rusted-tight or painted-over bolt, bolt extractors will break free. Reverse spiral flutes are designed to bite down to provide maximum gripping power. High carbon steel ensures longer life and greater durability. Universal lobular design fits all types of fasteners. 3/8" square drive For use with hand ratchets, impact wrenches, and air ratchets; hexagonal flats for use with flat wrench, pliers, adjustable wrench, sockets or Vise-Grip locking pliers. Set includes bolt extractors to remove bolt sizes: 8mm, 11mm, 14mm, 16mm, 19mm, 1/4", 5/16", 3/8", 7/16", 1/2", 9/16", 5/8", 11/16", 3/4". Packaged in a plastic case.