The Mercedes-Benz GLK350 outer and standard tail light assemblies utilize a P21W bulb size for replacement operations. The replacement chart covers vehicle production spanning 2010 to 2012.
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 position on the Mercedes-Benz GLK350 across the 2010-2012 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 corresponds directly to the single-filament construction of the bulb.
The ECE designation on the P21W indicates compliance with the United Nations Economic Commission for Europe lighting regulations, a standard adopted across European and many worldwide markets.
Because the P21W carries a single filament, it serves one lighting function per socket. Dual-function positions requiring both brake and running light output from a single housing would require a different bulb type.
The BA15s bayonet base is not interchangeable with the BA15d base, which is a dual-contact variant. Substituting a BA15d bulb into a BA15s socket is not mechanically compatible.