Installing shower filter - NPT adaptor for larger intake?
In your first picture, you are looking at a ball-swivel assembly that is part of the previous shower head that was attached.
If you take a wrench to the flat spots on the swivel-ball base (clearly seen in your first picture) and unscrew the swivel-ball, that entire assembly will come off and you will be left with the standard 1/2&quot; male NPT shower arm thread. NOTE- place a strap wrench or cushioned plier/wrench on the shower arm to hold it prior to attempting removal.