Mercedes-Benz G550 Back Up Light Bulb Size

The Mercedes-Benz G550 back up light utilizes a P21W bulb size for illumination purposes within the rear housing assembly. Data for the specified component covers a range from 2009 through 2018.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
2009-2018	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

Other Locations

Additional Notes

The Mercedes-Benz G550 uses the P21W bulb size for the back up light across all listed model years from 2009-2018.
The P21W is an ECE-standard bulb, meaning it conforms to the Economic Commission for Europe regulatory framework used in European and worldwide automotive lighting applications.
P21W bulbs operate on a 12-volt electrical system and draw 21 watts, which is typical for single-filament signalling applications such as reverse lights.
The P21W uses a BA15s bayonet base, where "BA" denotes a bayonet cap fitting, "15" refers to the 15mm base width, and the lowercase "s" indicates a single contact at the base.
Because the P21W carries a single filament, it is dedicated to one lighting function only, distinguishing it from dual-filament variants used in combined stop and tail light applications.
The BA15s bayonet mount is not interchangeable with BA15d bases, which carry two offset contact pins rather than one. Substituting a BA15d bulb into a BA15s socket is not compatible.
The consistent P21W specification across the 2009-2018 G550 model years indicates that the same replacement bulb applies to the full span of those vehicles.