Pentair R172008W White, Threaded Cap Replacement Rainbow Automatic Chlorine/Bromine Pool and Spa Feeder Threaded cap replacement Fits Pentair Rainbow automatic chlorine/bromine pool and spa feeder model 300, 302, 300-29X, 320, 322 Available in white color 3inch refers to the size of the pipe thread on the interior of the cap not the size of the cap itself.