Quoting kartorium:
where did you get the material gmp?
i got it from a plastic supply company here in denver me, and a friend got a big ass sheet for like 40 bucks.
We have made 2 sets so far one for his wrx and one for me, and lots to spare....
The material is a low density polymer cause i guess its not as loud when the rocks are hitting it when your rippin'.
The guys at a local rally shop use the same stuff, and they say the high density last longer its just really loud in a race car with no sound detaining.
hope that helps you can get this at most plastic dealers and it comes in a few different colors too