From Racingsportsconcepts.com:

After 3 years of constant painstaking research and development Racing Sport Concepts is proud to launch its new line of carbon fiber aerodynamic components for the next generation of high-performance automobile enthusiasts.  

What you are looking at is not just a factory replica or simple carbon replacement product, but a revolution in the aftermarket automotive industry.  For the last three years we have tested every piece of technology, CAD software, autoclaves, material vendors, painters, paint suppliers, aerodynamics experts, race car drivers, IMSA & Indycar crew chiefs, OEM engineers, everything possible to design the best possible product possible.  The RSC rear valence and its sister products are the culmination of that work.

We started by scanning the 991.2 GT3 and building our CFD model to match real world experience on the 911 platform by using aerodynamics experts that developed highly accurate CFD simulations from working for dozens of 911 cup car teams.  With our baseline accuracy significantly higher than if we had to develop a model from scratch and validate it all ourselves, while saving hundreds in thousands in development, we began to refine our design in the virtual wind tunnel.  Using dozens of simulations and design iterations to revise our designs to increase aerodynamic efficiency.