2002 Sable with 3.0 Duratec DOHC Thermostat

Guys,

Going to do a flush and thermostat replacement on my sons 2002 Mercury Sable 3.0 Duratec DOHC. I see on the different auto parts sites, that they have both paper and o-rings gaskets for the thermostat. Do I need both the paper and rubber o-ring or just one? If just one I would assume the o-ring is better? Any advice would be appreciated.

Thanks,

AJ