Custom Carbon Fiber Rear Diffuser for BMW 4 Series G26 420i 430i 435i M440i Doors Dual Exhaust Double Outlet

It replaces the plain lower valance on the BMW 4 Series G26 420i 430i 435i M440i Doors Dual Exhaust Double Outlet with a finned diffuser that cleans up the airflow leaving the rear bumper.

The clear coat is UV-stabilised, so the weave stays dark instead of fading to a chalky yellow under summer sun.

Fits: BMW 4 Series G26 420i 430i 435i M440i Doors Dual Exhaust Double Outlet

Moulded from the BMW 4 Series G26 420i rear bumper profile so the outer edges meet the bumper corners cleanly.

Undo the lower bumper fixings, offer the diffuser up, and re-use the original screws where the holes align – about an hour.

Quad-exit and single-exit cars use different cut-outs – confirm from the listing photos which bumper your car has.

Weave, finish and edge treatment are all chosen when you order: glossy 3K twill is the default, while matte, forged carbon, coloured clear coat and carbon-kevlar hybrids are produced on request.

• 3K twill, 6K twill, plain weave or carbon-kevlar hybrid
• Coloured tinted clear coat (red, blue, yellow)
• Logo application or badge cut-outs on request
• Gloss, matte, satin or forged carbon finish

Wash with a soft mitt and a pH-neutral shampoo, and avoid abrasive polishes or machine compounds that cut through the clear coat.

Our plant runs autoclave curing with logged temperature and pressure curves, so if a part ever fails we can trace the batch it came from.

Every unit is checked against a photo checklist – pinholes, weave alignment, mounting-hole position and clear-coat flow – before it is packed.

Small runs are quoted per piece; above roughly 50 pieces the tooling cost is absorbed and the unit price drops, so ask for a stepped quote.

Made to order in our workshop, typically 10-15 business days before it ships worldwide with tracking, backed by a 12-month warranty against manufacturing defects.

In the box: diffuser, screws, clips and a fitment card.