Heavy Duty Sizes: #1, #2, #3, #4 & #5 Reverse tapered flute for extra gripping power Spiral tapered flute for deep embedment which increases grip as the resistance increases Square end for use with tap wrench or spanner For the removal of damaged screws, stud & bolts. Left hand drill bits remove fasteners or creates the pilot hole required for a screw extractor. SCREW EXTRACTORS are engineered to remove the toughest damaged fasteners after the preparation of a pilot hole. The opposite direction flute enables the broken fastener to be gripped and wound out of the hole.