Cam Follower. Also known as "Valve Bucket" or "Tappet".
Located in the cylinder head directly above the valve & valve adjustment shim.
The camshaft pushes the bucket down to open the valves.
The new followers have a 4.5mm thick center where the shim rides.
Below are the original followers thickness where the shim rides.
The difference can be made up be using different valve adjustment shims.
(The original INLINE SIX followers are 5.5mm thick)
(The original V8 followers are 4.0mm thick)
Inline Six (3500, 3700, 4000)
GT V8 (4.2, 4.7, 4.9L)