The BOA 6 piece Damaged Bolt Remover Set is made from M3 Tool Steel and incorporates the patented reverse fluted spiral thread of the Grabit®. These unique bull-nosed extractors can be used with a standard wrench or in a drill (on reverse). Laser marked and supplied with a sturdy keep safe case these are simple to use; just drill and go! Fits: #1: 3-6mm (3/32 - 1/4in) #2: 6-8mm (1/4 - 5/16in) #3: 8-12mm (5/16 - 1/2in) #4: 12-18mm (1/2 - 3/4in) #5: 18-22mm (3/4 - 7/8in) #6: 22-25mm (7/8 - 1in)