Product Description Spark Plug Back Tap Thread Repair Tool 260mm M12 1.25mm Thread Chases from within, to reduce debriscontamination into the cylinder head Collapsible chaser head thread repair design reducesthe diameter of the reamer to allow it to actuallybypass the damaged thread & enter the cylinder tochase the thread from the inside to the outside Inside to outside thread repair method reduces thechance of swarf & debris entering the cylinder Easy & safe thread repairs