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:Square screw extractors are used when a screw or bolt has broken off while still in the fastening hole5 Piece set includes #1 #2 #3 #4 and #5 screw extractorsEasily removes 3/16-Inch to 5/8-Inch broken bolts and screws Made of hardened tempered alloy steel