It is the more expensive one like rp17 says; more details here:
101 Projects for Your Porsche Boxster: Project 9: Air / Oil Separator Parts
Instructions here:
Pelican Technical Article: Boxster Air / Oil Separator Replacement - 986 / 987
I think that other $37 part goes in the oil sump pan but I'm not sure, I don't recall hearing a lot about that part.
Steve