What is the correct term for this part.
I believe you are referring to the filter drier
Correct. Thanks. the name slipped my mind.
Not that it really matters, but that is a suction line filter.
There is also a filter/dryer that is installed on the small liquid line.
This one needs removal before it leaks refrigerant (if not already leaking).
A few more notes:
A suction line filter should not be installed on a heat pump on the external piping of the unit. It must be between the compressor and the reversing valve.
A liquid line dryer should never be located between the compressor and the condensing coil.
Suction line filters can be removed and not replaced. They are used for contamination clean up after compressor failure to protect the new compressor from the crap of the old one.