IRWIN BOLT-GRIP Impact Performance Series Deep Well Extractors feature reverse spiral flutes and extended reach to fit over exposed studs and easily grip and remove recessed fasteners including broken, damaged, or rusted nuts, bolts and screws. While they're built for maximum durability and long life with impact tools, they also work perfectly with rotary drills and drivers. They're manufactured with high carbon steel ensuring longer life and greater durability and the universal lobular design fits all types of fasteners. These bolt extractors also include a black oxide finish that resists corrosion and extends life of the tool. The 3/8" square drive enables use with impact wrenches and the extractors are also compatible with 1/4" impact drivers when used with an adapter. If 1/2" drive size: The 1/2" square drive enables use with impact wrenches and the extractors are also compatible with 1/4" impact drivers when used with an adapter.