Powerbuilt 648639 1/4" to 3/4" Stud Extractor For removing broken or seized studs, bolts, etc. from 1/4" to 3/4" diameter Knurled roller uses cam action to grasp stud firmly while minimizing damage For removing broken or seized studs, bolts and the like from 1/4 inch to 3/4 inch diameter Knurled roller uses cam action to grasp stud firmly while minimizing damage Use with 1/2 inch drive ratchet