Injector Cap, Autotrol 1000218 1000269

Also, Fleck 5810, 5812 list this "blank cap" as a replacement part.  
Includes O-ring 1010110 ( AP2F )

Replaces the "A" (1000217 ), "B" ( 1000218 ), "C" ( 1000219 ), or "D" ( 1030303 ) used on some caps between 1996 - 2006.
Also, the Refill Cap (Part number 1033441) for a Autotrol Performa FA valve.
* The Injector CAPS are all the same now.
Backwash Plug and Injector Cap Removal Tool