Watts RETRO 800M4 FR 1" 0887718

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.  

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.