OmniSwivel 9/16"-18 M to 9/16"-18 M LP adapter.
This adapter is the same thread as a regulator second stage on both ends. It is used to convert the end of a regulator hose into a male 9/16" fitting.
If you are purchasing the Y-Block( MB-Z2) and intend on connecting it to a regulator LP hose, you will also need this adapter.