Piston

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.

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.