Qbace 14mm Spark Plug Re-thread Rethread Rethreader Repair Tap Tool Reamer Inserts Kit Includes combination tap, reamer, and locking compound. Includes insert sizes: 3/8-Inch, 7/16-Inch, 1/2-Inch and 3/4-Inch Tap is designed for aluminum heads only Designed for professional auto mechanics and heavy duty applications Spark plug thread repair tools kit.