G22/G23 4 Series PSM Carbon Fiber DiffuserCenCal Motorsport PSM Style Carbon Fiber Rear Diffuser BMW G22 G23 4 Series Transform the rear profile of your BMW with the CenCal Motorsport PSM Style Carbon Fiber Rear Diffuser, engineered for the G22 Coupe and G23 Convertible 4 Series. Inspired by the aggressive design language of high performance motorsport aero, the PSM diffuser enhances both the appearance and aerodynamic flow of your vehicle giving it a lower, wider, and more dynamic stance.