The Mercedes-Benz R500 tail light requires a P21W bulb size for proper installation and function within the rear lighting assembly. Data for the specified component covers the 2006 to 2007 range.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21W is the bulb type specified for the outer tail light of the Mercedes-Benz R500 across the 2006-2007 model years.
The P21W is an ECE-standard single-filament bulb rated at 12 volts and 21 watts, mounted on a BA15s bayonet base.
The BA15s base designation indicates a single-contact bayonet fitting with a 15mm base width, which is not interchangeable with dual-contact BA15d bases used in other automotive applications.
As a single-filament bulb, the P21W serves one lighting function per unit, distinguishing it from dual-filament types that handle two functions such as tail and brake lighting within a single bulb.
The ECE standard classification means the P21W conforms to United Nations Economic Commission for Europe regulations, a specification framework adopted across European and many international markets.
At 21 watts, the P21W falls within the higher output range for single-filament signal bulbs, a wattage associated with turn signal and brake light applications rather than lower-draw parking or position light duties.