Man, can't believe I didn't know that was just an O-ring.
That is the source of my coolant leak. I just replaced my rad hoses because i thought the lower was leaking and i couldn't get it to seal. Oh well, the new ones look nice.
Any trick to replacing this, i'm going to go attempt it now.

Answered my own question.
The hardline pulls right out. Off to Napa to get a replacement.

yep.