Part number 42-2333B-K is a Hydro Quip Uni-Nut Kit for 3-inch heater tubes.
This part is a universal replacement union nut designed to provide a secure connection for heater tubes and is compatible with various brands that use 3-inch heater housings.
The following manufacturers are known to use heater systems, controls, or components that are compatible with this part:
Hydro Quip: The manufacturer of this specific Uni-Nut part.
Balboa Water Group: The Uni-Nut is compatible with many Balboa heater assemblies and control systems.
Gecko: Compatible with some Gecko heater systems.
Coleman Spas: Used with compatible heater and control systems in certain models.
Leisure Bay: The Uni-Nut is an available replacement for their 4kW heater assembly systems (e.g., E2400-1001 model).
Spa Builders: Compatible with their heater unions.
Correctech.
Spanet.
Because this is a standardized plumbing fitting, it is widely used as a replacement part across many different spa brands that use a standard 3-inch heater housing with a 2.5-inch male buttress thread (MBT) connection.