This relief valve repair kit fits the old style 4 - 6" Watts 909 Series reduced pressure zone (RPZ) backflow preventers. The "old style" relief valve was produced from 1979-1989. The "new style" replaced the "old style" in 1989 and is still currently in production. An easy way to determine which relief valve you have is to check the relief valve body material. The "old style" relief valve body is constructed bronze and the "new style" body is epoxy coated cast iron. This relief valve kit is for the "old style" bronze body relief valve. No special tools are required for servicing. Genuine Watts replacement parts.