The Mercedes-Benz R320 tail light requires a P21W bulb size for proper installation and function. Data for the specified lighting component covers the period from 2007 through 2009.
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 positions on the Mercedes-Benz R320 across the 2007-2009 model years.
The P21W is an ECE-standard single-filament bulb rated at 12 volts and 21 watts, designed primarily for signalling functions such as brake and turn signal applications.
P21W bulbs use a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar width. The single-contact design distinguishes it from dual-filament variants that share a similar physical form.
Because the BA15s base is a single-contact fitting, it is not interchangeable with BA15d base bulbs, which carry two filaments and two contact points at the base, despite the two types sharing a similar overall profile.
The ECE designation on the P21W indicates the bulb conforms to United Nations Economic Commission for Europe regulations, a standard adopted across European and many worldwide markets for automotive lighting.