Left-hand spiral for locking on to rounded ,damaged bolts for easy grip of stud, bolt or nuts.Four metric sizes: 17mm, 19mm, 21mm, 22mm and a metal rod to tap/knock the bolt out of the extractor once the bolt is removed.Made from chrome molybdenum steel with a black oxide coating for greater strength and durability and to prevent corrosion.1/2″ square drive for use with flat wrenches, pliers, socket wrenches, adjustable wrenches, Vise-Grip locking pliers, hand ratchets or impact wrench guns and air ratchets.Supplied in a heavy duty, durable and portable case for extra long life.