The Mercedes-Benz R350 tail light requires a P21W bulb size for proper installation and function within the rear lighting assembly. Available data for the bulb specifications covers the range from 2006 to 2010.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz R350 outer tail light uses the P21W bulb across all listed model years, spanning 2006-2012.
The P21W is an ECE-standard bulb, meaning it conforms to European and international automotive lighting regulations rather than SAE standards used in North American specifications.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is typical for incandescent stop, tail, and turn signal applications.
The P21W is a single-filament bulb, meaning it serves one lighting function per bulb rather than combining two functions such as running light and brake light into a single unit.
The P21W uses a BA15s bayonet base, where "BA15" refers to the 15mm bayonet cap width and the lowercase "s" denotes a single contact at the base, corresponding to its single-filament design.
The BA15s base is not interchangeable with the BA15d base, which carries two contacts and is used for dual-filament bulbs. Substituting one for the other is not possible without modification.