Square flute screw extractors are used when a screw or bolt has broken off while still in the fastening hole. Ideal for thin wall extractions. Will not spread the wall as it extracts. Thin-gentle removal. Product Features:Easily removes 3/16-Inch to 5/16-Inch broken bolts and screwsUse 9-64-Inch left handed drill bit to drill hole this will help loosed bitIdeal for thin wall extractionsWill not spread the wall as it extracts