2017-2019 Audi A4/S4 — KB & S4 Style Rear Diffuser

Upgrade the rear of your 2017-2019 Audi A4 / S4 with your choice of two rear diffuser styles. Both are crafted from high-quality ABS plastic and designed for a clean, bolt-on fit using factory mounting points.

Style Options:

• KB Style — Aggressive multi-fin diffuser available in Black (primer-ready) or Carbon Fiber (hydrographic hydrodip). Fits both S-line/S4 and Non S-line trim levels.
• S4 Style w/ Exhaust Tips — OEM+ diffuser with integrated dual exhaust tip surrounds for a factory S4 look. Available for S-line and S4 trim levels only.

Key Features:

• Material: High-quality ABS plastic — primer-ready, paint to match or custom finish
• Designed for 2017-2019 Audi A4 / S4 using factory mounting points; may require fitment and trimming adjustments based on vehicle trim options — professional installation recommended
• Bolt-on installation — no cutting of the factory bumper required for standard fitment
• Fits A4 and S4 models only — not compatible with RS4

Fitment: 2017-2019 Audi A4 / S4 — B9. KB Style fits both S-line/S4 and Non S-line. S4 Style w/ Exhaust Tips fits S-line and S4 only (requires factory S-line rear bumper configuration).

The Carbon Fiber finish is a premium hydrographic carbon fiber hydrodip, pre-applied over ABS — no painting required.

Production & Lead Time: These rear diffusers are custom-manufactured to order. Please allow 1–2 weeks for production before your order ships. Orders cannot be modified or cancelled once production has begun.

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Optional Exhaust Tips Upgrade

Complete your rear-end refresh by pairing this diffuser with matching stainless steel exhaust tips. Available in two finishes to complement your build:

• With Silver Tips — Polished stainless steel, mirror finish. OEM+ appearance that blends seamlessly with factory exhaust setups.
• With Black Tips — Powder-coated stainless steel with matched internal polish. Aggressive stealth appearance for blacked-out builds.

Tips ship as a matched pair with slip-on collars sized to fit factory exhaust piping. Installation is bolt-on / slip-on — no cutting or welding required for most factory exhaust configurations.

Select "With Silver Tips" or "With Black Tips" above to add tips to your diffuser order. Choose "No Tips" if you're keeping your existing exhaust setup.