2018–2019 Audi A4 B9 Sedan Rear Bumper Diffuser – Carbon Fiber

Transform the lower rear profile of your Audi A4 B9 Sedan with this carbon fiber rear bumper diffuser. Spanning 130 cm across the lower bumper, it adds width and a more aggressive lower rear appearance with a deep gloss carbon black finish that visually lowers and widens the rear stance.

Build

• Material: Genuine carbon fiber, autoclave cured and vacuum moulded using a 3D design and CNC moulding process for precise diffuser geometry, consistent panel quality, and an authentic weave appearance over carbon-look ABS or fiberglass alternatives
• Surface finish: High-gloss epoxy-polished finish in carbon black that showcases the natural carbon weave and resists UV exposure, moisture, and road debris through sustained outdoor and driving use
• Configuration: Single-piece diffuser for the lower rear bumper
• Panel width: 130 cm across

Design & Aerodynamics

• Aggressive stance: Diffuser profile adds width and visual weight to the lower rear for a more planted, track-inspired rear end
• Comprehensive coverage: The 130 cm span covers the lower rear bumper for a complete, finished rear-end upgrade
• Carbon aesthetic: Directional weave and gloss black finish complement the factory B9 bodywork for a coordinated, motorsport-grade look

Fitment

• 2018–2019 Audi A4 B9 Sedan
• Standard A4 only — does not fit the S4, which uses a different rear bumper
• Fits the factory rear bumper only — not compatible with aftermarket bumper configurations
• Body style: Sedan only — not confirmed for Avant or Allroad body styles

Package Contents

• 1 × carbon fiber rear bumper diffuser
• Pre-applied adhesive tape for installation

Installation

• No-drill, adhesive-mounted: Installs with the included adhesive tape — no drilling and no permanent modification to the factory rear bumper
• Surface prep: Thoroughly clean, degrease, and dry the rear bumper before fitting to ensure maximum adhesion
• Alignment: Dry-fit and check the diffuser sits centred and even across the bumper before final adhesion
• Professional installation recommended for correct panel alignment and finish quality

Before You Install

• Confirm your car is a standard A4, not an S4 — this is moulded to the A4 rear bumper and will not fit the S4
• Verify your body style is the Sedan before ordering — fitment is not confirmed for the Avant or Allroad
• Work in moderate temperatures and allow the adhesive to cure fully before washing the car
• Installation is reversible, but adhesive removal and re-prep may be required if the diffuser needs repositioning