Seibon 18-20 Subaru WRX / STI Carbon Fiber Rear Diffuser

Seibon Carbon Fiber Rear Diffusers are engineered to do more than just look aggressive—they actively manage airflow to reduce drag and improve rear-end stability. Drawing on motorsport principles, Seibon’s diffusers are designed to smooth and accelerate underbody airflow as it exits the rear of the car, helping to minimize turbulence and lift at high speeds.

Each diffuser is crafted from premium aerospace-grade carbon fiber using Seibon’s signature vacuum-infused construction process. This results in lightweight panels with exceptional stiffness, strength, and surface consistency. The signature 2x2 twill weave is finished in a high-gloss UV-resistant clear coat that resists yellowing and oxidation, maintaining its striking appearance over years of use.

Depending on vehicle and application, Seibon’s carbon fiber diffusers may feature integrated fins, vent channels, or sculpted contours designed to optimize the aerodynamic profile of the vehicle. These elements are not just for show—they’re engineered to improve rear-end downforce and promote better airflow separation, especially on high-performance builds and track applications.

Whether you're building a competition-spec car or a street machine with show car styling, a Seibon diffuser delivers both form and function. It’s the perfect way to tie together your carbon fiber aero upgrades and reinforce the performance DNA of your vehicle.

• Aerospace-grade carbon fiber construction with UV-protected clear coat
• Functional aerodynamic design helps reduce drag and improve high-speed stability
• Vacuum-infused resin system ensures strength, stiffness, and lightweight performance
• Integrated fins or venting features may enhance rear downforce and airflow separation
• Motorsport-inspired styling elevates rear-end appearance while improving performance