Presto 090104 No. 4 Screw Extractor

76mm overall length, 33mm flute length.
Recommended pre-drill size 1/4"

Used expressly for removing broken or seized screws and studs. They are left-handed, for use on right-handed threads. The screw is first drilled out to the proper diameter for that extractor. The extractor is then inserted into this hole and turned counter-clockwise using a tap wrench. As the extractor is turned the flutes on the tool dig into the screw, causing it to lock tightly and apply sufficient torque to remove the screw.