Stud extractors enable you to insert and extract stud bolts. They have a square drive so can be used with a hand ratchet (socket wrench).
They have one eccentric knurled wheel which grips an internal fluting.
The eccentric knurled wheel tightens against the stud bolt, keeping it in place.
Roll type stud extractors
This type of extractor also lets you extract and insert stud bolts. It can unscrew both right and left hand threads.
It has 3 rollers that grip the stud at 3 points during removal.
It contains a 13 mm (½”) square drive or hexagonal end to fit either a hand ratchet (socket wrench), mole grip pliers, spanner or adjustable spanner to give additional leverage for those stubborn studs.