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. When you are faced with a rounded off rusted tight or painted over bolt, bolt extractors will break it free. Set includes plastic case 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 bolts sizes: 11mm, 14mm, 16mm, 3/8", 7/16", 1/2", 9/16", 5/8" in drive size 3/8".