This 1/2 to 3/4 in second check replacement kit, for series SS007M3, is used to prevent the backflow of contaminated water into the potable water supply. It consists of a seat, seat O-ring, disc assembly and spring, check cage and cover O-ring. It is ideal at referenced cross-connections identified as non-health hazard applications. Check with local inspection authorities for installation requirements. WATTS® Second Check Kit, For Use With: Model 007/LF007 1/2 to 3/4 in Double Check Valve Assemblies, Domestic