The Tools make it possible to do a first time repair with just 1 insert if you already have the Triple oversized kit.
Add-on kit: This is a Ford Z-Tech ADD-ON Kit P/n 5678-Z with 24mm length inserts that is used in conjunction with the p/n 5600 triple over-sized. This kit only includes the Reamer and Tap from the Original 5553 kit so you can use the Original Z-Tech style inserts P/n 51460  (5) included with out having to go Oversized on a first repair. Instructions here.  If you are just trying to do the more common Ford Spark plug repair with the 16.8mm inserts See kit P/n 5678