The Mercedes-Benz CLK350 front fog light uses H7 and H11 bulb sizes, while the rear fog light requires a P21/4W bulb size. The replacement chart covers 2006 through 2009 model years with corresponding bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CLK350 front fog light uses two different bulb types depending on the model year: the H11 for 2006 and the H7 for 2007-2009. These two bulb types are not interchangeable, as they use different bases and are physically incompatible with each other's housings.
The H7 is a single-filament halogen bulb rated at 12V and 55W, built to the ECE standard with a PX26d base. It holds approval for use in Europe, worldwide markets, the United States, and Japan.
The H11 is also a single-filament halogen bulb rated at 12V and 55W, built to the ECE standard with a PGJ19-2 base. It holds approval for use in Europe, worldwide markets, and the United States, though it is not listed as approved in Japan.
Although the H7 and H11 share the same voltage and wattage ratings of 12V and 55W, their base types differ. The PX26d base of the H7 and the PGJ19-2 base of the H11 are distinct connector formats, making cross-substitution between the two physically impossible without modification.
The rear fog light specification for the CLK350 remains consistent across all listed years, with the P21/4W bulb used from 2006-2009.
The P21/4W is a dual-filament signalling bulb rated at 12V with a split wattage of 21W and 4W across its two filaments. It uses a BAZ15d bayonet base and conforms to the ECE standard for European and worldwide markets.
The BAZ15d base of the P21/4W is an offset-pin bayonet fitting. The asymmetric pin placement is a deliberate design feature that prevents incorrect installation of the bulb in its socket.