5600 Softener Piston Assembly 60102-00.
Used on all Fleck 5600 softener valves since 1979.
Standard Softener Piston Assembly =
Includes sub-parts 13001,13446,12953,10696,13247,13363,13296
The color of the Teflon coating of the piston may be Green or Gray.
It's only the "top" end plug that is color coded to help identify any "difference" between the various versions.
As shown in the 4th photo, the older end plugs were more round at the top, and the leaking occurs due to wear of the Teflon coating on the shaft and not just the seal o-ring in the end plug. Thus the reason for recommending replacing the entire Piston Assembly and not just the "end plug" portion.
Also, used on some Fleck 5600 Filter Valve applications instead of the longer backwash Filter Piston version ( 60102-10 ) with the black end cap.
And there is a "Low Water" version ( 60102-20 ) with the gray end cap ( used mostly on city water in California ) and not recommended on well water.
To learn more about the 3 common types of Pistons, see:5600 Piston Assembly Types - Softener - Filter - Low Water, Piston Assembly 60102-00, 60102-10, 60102-20, What is the Difference?Cross reference European ( U.K. ) part number XF24116, Hydro-Quad reference 40-5010
CUNO ( Aqua Pure ) water softener piston cross reference PN 55640-64