[T3] Dash fresh air vents

[Ralph Tree]

Hi All,
I've got a quick question that I haven't been able to find an answer to. What are the tubes that connect to the fresh air vents on the dash made out of? Are they supposed to be hard tubes or some type of fiberboard tubes? It's just one of those little details that I would like to be right.
Any help is appreciated

Thanks
Ralph Tree

Ogden, Utah