The Blue Spot Tools 6Pce Broken Bolt and Screw Extractor Set is manufactured from hardened alloy steel for durability. The set comprises of 5 extractors of various sizes for the removal of screws/bolts when the head has become damaged. Insert the extractors into a pre-drilled hole within the screw or bolt stud, due to its deep reverse thread it will remove the screw or bolt stud easily. The hex shank enables the extractors to be quickly fitted to any 1/4" power bit adaptor. Reverse thread for screw or bolt stud removal 1/4" Hex Shank Removes Broken Studs and Screws easily PACKAGE CONTENTS 1x 3.1-6.3mm (1/8"-1/4") , 1x 6.3-7.9mm (1/4"-5/16") , 1x7.9-11.1mm (5/16"-7/16") , 1x11.1-14.2mm (7/16"-9/16") , 1x14.2-19mm (9/16"-3/4")