Spark Plug Thread Repair Kit M12x1.25 Inserts and M14x1.25 Tap Kit Spark Plug Thread Repair Tools Spark Plug Tap Inserts Thread Repair Tool Gasoline Engine Repair Tools. Comprehensive Repair Kit: The spark plug thread repair kit includes 10 M12 x 1.25 thread inserts and an M14 x 1.25 tap, providing a professional-grade solution for thread repair needs.