APR Vortex Generators help to guide the airflow on cars with very steep drop-off angles between the roof and the rear window. Airflow has a tendency to become turbulent as it separates from the surface of the car in this region. This turbulent air causes drag and reduce the effectiveness of a rear wing. The APR Vortex Generator helps to reduce drag and improve the effectiveness of the rear wing by delaying the air flow separation and reducing turbulence.