This APR Performance 2014-2019 Porsche GT3 Carbon Fiber Rear Diffuser will only NON-RS. This rear diffuser will work on both the 991.1 and 991.2 GT3 models. Diffusers work in conjunction with other aerodynamic components of a car to help produce downforce. Because a car displaces air as it moves forward, the air molecules in the rear of the car get disrupted causing a vacuum of low-pressure air. To help channel the high-speed airflow coming from underneath the car, diffusers redirect the high-speed airflow to transition smoothly transition into the low-pressure vacuum in the rear. This encourages a smoother flowing airflow underneath the car and allows better performance from other aerodynamic components such as aerodynamic wings.