The Mercedes-Benz R350 front fog light requires an H7 bulb size while the rear fog light uses a P21W bulb size. The replacement chart covers vehicle production spanning 2006 to 2012 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 R350 front fog lights use the H7 bulb across the 2006-2010 model years.
The H7 is a single-filament halogen bulb rated at 12V and 55W, fitted with a PX26d base. It is manufactured to ECE standards and holds approval for use in Europe, worldwide markets, the United States, and Japan.
The Mercedes-Benz R350 rear fog lights use the P21W bulb across the 2006-2012 model years.
The P21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BA15s bayonet base. It is manufactured to ECE standards and is used across European and worldwide markets.
The BA15s bayonet base of the P21W differs from the PX26d pin base of the H7, making the two bulb types physically incompatible with each other's sockets.
Both the H7 and P21W operate on a 12V electrical system, which is standard in passenger vehicles of this class.
The H7 front fog bulb draws 55W, while the P21W rear fog bulb draws 21W. The difference in wattage reflects the distinct functional roles of forward illumination versus rearward signalling.
The single-filament construction of both the H7 and P21W means each bulb serves only one lighting function, with no secondary filament for an additional mode such as a brake or running light.