Double-edged bolt & screw extractors from Knipex, No. 9R 471 901 3. For more information on this product check out www.VehicleServicePros.com/10830184.
Photo credit: Knipex
Knipex's double-edged bolt and screw extractors, No. 9R 471 901 3, can remove damaged screws, studs and bolts and is servicable for years of use. Extractors in this set assist with removing damaged screws and bolts without damaging the threads on both right- and left-handed thread applications. Non-slip and double-edged engagement removes even the toughest frozen bolts. The tool has four double-edged cutting / gripping edges. Simply drill the right sized hole into the frozen bolt, hammer in the extractor, and turn it out with a wrench or ratchet. Made in Germany.