When nox sensor nox catalytic converter performance matters, the TOPRAN 121 557 delivers — built to the same dimensional and material standards as the original part it replaces. The part is built to the following specification: Fitting Position: 178, Thread Size: M 20, Spanner Size: 22, Cable Length [mm]: 910 mm, Supplementary Article/Supplementary Info: 37. Each dimension is checked against the OEM reference to ensure the component seats and functions correctly first time. Compatible with VW vehicles; use the vehicle selector above to confirm exact fitment for your make, model, and engine variant. Fitment data is sourced from TecDoc, the authoritative European parts catalogue. This part supersedes original equipment references: 04L 907 807AT, 04L907807AT, 04L 907 807EB, 04L907807EB and 34 more. Matching these numbers confirms a like-for-like replacement with no loss of function. TOPRAN is a recognised supplier of automotive replacement components to independent workshops and dealer networks across Europe. All parts are sourced from authorised distribution channels and carry full manufacturer traceability — you receive exactly the same component supplied to professional garages and dealer workshops. If fitment or specifications do not match your vehicle, our technical team can help identify the correct alternative — use the vehicle selector or contact us with your VIN for a guaranteed-fit recommendation. Replacing worn components on schedule preserves your vehicle's safety, reliability, and resale value — and aftermarket parts from established brands deliver OEM-equivalent performance at a fraction of the dealer price. Every part is dispatched from our UK warehouse with a 30-day money-back guarantee and free hassle-free returns.

TOPRAN, part of the Hans Thomsen Group headquartered in Hamburg, Germany, is a growing independent aftermarket brand focused on providing quality parts at accessible prices. TOPRAN offers a comprehensive range covering engine, cooling, electrical, braking, and body components for European vehicles. All TOPRAN products are manufactured to meet OE specifications and undergo quality testing before distribution. Combining German quality management with competitive pricing, TOPRAN is an excellent choice for cost-conscious motorists and workshops who do not want to compromise on part quality.