[fearstang]

can anyone tell me what the real name for the black thing (red arrow)atthached to the rear bumper and goes under the rear of the 05 mustang GTR. and what is it made of and is there any special angles the fins are positioned in. any help would be greatly appreciated.

[Jarrett]

I am pretty sure it is a diffuser, and is used to clean up the air coming out from underneath the car.
No idea of the material, or the angle of the fins but they look to be made of plastic and run perpedicular to the rear bumper cover.