This innovative, Impact stud extractor is fully adjustable and can be used with air tools or standard hand tools on 6-12mm studs. It will effectively work on and remove threaded, broken, rusted, stripped or smooth studs.
Laser 3986 - Impact Stud Extractor 1/2" Drive. A Set of 2 pieces is also available (3/8" & 1/4" drives)
See the How Do I Remove Broken Studs? article in the Technical Articles section