Hayward Universal H200FD Negative Pressure Indoor Vent Adapter (UHXNEGVT12001) aquastar A part like this is

A part like this is useful because it helps restore the threaded connection structure used by the split nut assembly

and FC-9845 reference give this part practical value because DE filter assemblies work best when the replacement matches the original size and internal port arrangement closely

or no longer communicates accurate temperature protection data

This type of replacement is especially useful when the trap housing remains serviceable and the real weakness is centered on the basket itself

It is a practical service choice when restoring reliable heat in a supported low flow application is the main repair priority

Hayward Universal H200FD Negative Pressure Indoor Vent Adapter (UHXNEGVT12001) aquastar A part like this isThe Hayward indoor vent adapter is designed for compatible Universal H200FD heater applications where a negative pressure indoor vent system needs the proper transition fitting. An adapter like this is useful because it helps connect the heater to the venting system in a way that supports a cleaner and more appropriate installation. This replacement is especially useful when the original adapter is damaged, missing, or not suited to the intended vent