2005 Captiva 232 interior question

I have a 2005 Captiva 232 we bought it from the original owners, they were a little rough on the interior.
currently my curved bench seat back has a blue plastic support structure that has 212 cut into along with all the clip holes instead of marine plywood. what material was used for the seat backs on these so i can replace them.
thanks guys
currently my curved bench seat back has a blue plastic support structure that has 212 cut into along with all the clip holes instead of marine plywood. what material was used for the seat backs on these so i can replace them.
thanks guys