Lower Back interior panel replacement?

[m2bandit]

I have the plastic panel that goes just below the window but what goes below that?  I can't seem to find a picture that clearly shows it but it looks like carpeted board?
What is it? what does it look like?

 

I have an 88 bucket seat gray interior chief.

[jdog]

cardboard carpeted

 

[m2bandit]

13 minutes ago, jdog said:

cardboard carpeted

 

Thank you!

[jdog]

no problem

[ghetdjc320]

I just made a replacement for mine using some 1/2” birch ply that I bedlined. Works great and is a nice mounting point for storage and organizing behind the seat.