RETRO 800M4 FR 1". Kit includes float disc assembly, vent spring, bonnet and bonnet o-ring.This kit is to convert a regular 800M4 to a freeze resistant (FR) version. Really, the only difference is the vent float which is sold as a kit by iteself. It is part number 0887715, RK 800M4 FRV 1"
The difference in the vent float between the two versions is the FR version has a stem in the center with a spring and a "BB" like ball that allows for expansion.