Milltek Sport Race Axle-Back Exhaust Rear Silencer/Back Box with Polished Twin Tips for BMW 1 Series M135i F20/F21 2012+ (3 & 5 Door) - T304 Stainless Steel Performance Rear Muffler Upgrade N55

Milltek Sport Race Rear Section with Mirror-Finish Tailpipes for BMW 1 Series M135i F20 F21 2012+

Transform the sound and character of your BMW M135i with Milltek Sport’s race-level rear section. This direct-fit rear muffler replaces the factory back box on M135i F20 and F21 models and unlocks a deeper, harder-edged tone with sharper throttle response and a cleaner, freer-breathing flow path. Crafted in the UK from premium T304 stainless steel with beautifully polished twin outlets, it is the ideal upgrade for drivers who want a more engaging soundtrack without compromising quality.

Key benefits

• Race sound level for a more assertive, motorsport-inspired note under load
• T304 stainless construction for long-term corrosion resistance and durability
• Precision-formed pipework designed to reduce restriction and improve gas speed
• OEM-style hangers and flanges for a straightforward bolt-on replacement of the stock rear box
• Mirror-polished tips that elevate the rear styling on both 3 door and 5 door 1 Series
• Engineered and built in the UK by Milltek Sport

Compatibility

Designed to fit the following models:

• BMW M135i F21 3 door 2012 onwards
• BMW M135i F20 5 door 2012 onwards

How it sounds and performs

Expect a stronger, more purposeful tone with a crisp crackle on upshifts and a richer idle, while cruising refinement remains perfectly usable for daily driving. The free-flow rear section reduces factory silencing and helps the turbocharged six sing, giving the M135i a soundtrack that matches its performance.

Why choose Milltek Sport from MJ Modifications

We have fitted this rear section to customer M135i cars in our workshop and feedback has been consistently positive. Owners love the quality, the fit and the way the Race sound setting brings the car to life. Built from high-grade stainless steel with high-quality welds and neatly finished, polished outlets, it is a premium upgrade that looks as good as it sounds.

Professional fitting

Want it installed by experts We offer fitting at MJ Modifications in Warwickshire. Request a quote at info@mjmodifications.co.uk.

Search-friendly terms customers use

BMW M135i F20 F21 rear muffler, M135i sports back box, BMW 1 Series M135i 2012 performance rear section, Milltek Sport axle back M135i, stainless steel rear box M135i, twin polished tailpipes M135i, BMW 1 Series M135i sound upgrade, UK made T304 M135i rear section, direct fit rear silencer M135i, performance tailpipe upgrade M135i.