Nut used on 1650 Brine Valve Assembly GFN 19625 sold in kit 60900-40
( Includes parts labeled A, B, and C in the diagram ).
The BLFC fitting and Brine Valve ( 1650 ) are normally reused.
Or they can be purchased separately.
This plastic Brine Valve Assembly ( 3/8" tubing ) is used on the newer Fleck 2510, 2750, and 2850 Valves.

Also used with 3/8" Brine Shut off 2310 ( 60014 ).