The filter port nut (FAPNUT) and filter port seal (FAPSEAL) are used to seal off the pressure gauge ports on top of super filters when not in use. The nut and seal are stock on most super filters, adding the pressure gauges is optional.
To seal off the pressure gauge port, simply remove the 1/4" pressure gauge and 1/4" female coupler, exposing the male port threads. Then place the rubber seal inside the nut and tighten over the port threads. The nut and seal must be used together to create a watertight seal.
The filter port nut and seal can be used with Amiad Super T Filters and Arkal Super Disc Filters.