The “Race” Version of the rear diffuser is for use on vehicles without rear exit exhaust (ie: Dumps or Side Exit). The diffuser is the full width of the rear bumper. The Base is constructed 1/4 inch ABS plastic while the Fins are made from an Aluminum Composite Material (ACM) this gives the fins a high quality smooth black finish. The diffuser does not need to be painted and will never rust. In the event of damage the Fins are easily replaceable with screws going into the top of the fins giving our diffusers a very clean appearance. Purchase includes all mounting hardware and instructions.