This Ford spark plug kit p/n 5553 will repair holes as large as .660 inches or 16.8mm. M14x1.25 for 2 and 4 valve engines. Includes 5 inserts P/n 51459 half threaded spark plug inserts. Because the 5553 kit uses the half threaded inserts, The insert can accept Full and half threaded spark plugs. This is very important because you would never want to put a "half threaded Spark plug" into a full thread insert because it would stick up. This is why the 5553 is preferred because it can except both style spark plugs. Instructions included in kit.  If you need a kit to repair holes larger than .660 inches see  Ford Triple Oversized p/n 5600