B Body AC Duct Foam Seal

I am installing the AC plenum and center duct on my 70 Superbee. They look like this.



Do both mating surfaces get one of these seals or is there just one sandwiched between them?


Thanks!

A single seal is used between the two individual duct surfaces.

Thank you. I have a hodgepodge of parts and there are gaskets on each. I noticed that there is adhesive film on the duct side of one of my gaskets so I am assuming they were attached to the duct and not the plenum?