RENNtech | Carbon Fiber | Rear Diffuser | 197 - SLS AMGRENNtech Carbon Fiber Rear Diffuser for the 197 SLS AMG Our rear diffuser is the companion component to the front splitter and functions to decrease drag and increase down force by improving the underbody airflow and its transition to ambient air. As with the front splitter, our rear diffuser is manufactured using the high quality prepreg carbon fiber and is a quick and easy install that requires no modifications to the SLSs rear bumper or underbody.