Full thread Taper seat insert. Note: If using kit p/n 5553 the instructions say to only go 10 turns for the p/n 51459 half threaded insert but with the 51457A "Full thread" you will need to go 20 full turns to cold roll the bottom few threads to lock the insert in place. You would also need setting tool ring 51484A Insert requires sealer 6020 on external threads.