This FreshWater Ag+ gray standpipe cap holds the filter in place on a gray colored standpipe. This gray standpipe cap identifies the correct standpipe (if your spa model has more than one filter) to insert the Fresh Water Ag+ Silver Ionizer into all 1992-current Tiger River spas, all 1990-current Hot Spring spas, all 2003-current Hot Spring Solana spas and 1998-2002 Hot Spring Hot Spot spa models.
