Mercedes-Benz G550 front fog light bulb size is H11 and rear fog light bulb size is P21W. The replacement chart covers 2009 to 2018 production years with bulb specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz G550 uses the H11 bulb for the front fog light position across the 2009-2018 model years.
The H11 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PGJ19-2 base, and rated under the ECE standard recognized in Europe, worldwide markets, and the United States.
The PGJ19-2 base is a keyed projector-style connector, which physically prevents substitution with other H-series bulbs that share similar wattage or voltage ratings but carry different base configurations.
The rear fog light position on the G550 uses the P21W bulb across the same 2009-2018 model years.
The P21W is a single-filament signalling bulb rated at 12V and 21W, mounted via a BA15s bayonet base, and also governed by the ECE standard.
The BA15s bayonet base features a single contact pin offset to one side, which distinguishes it from the dual-pin BA15d base and prevents cross-installation between the two types.
Both the H11 and P21W operate on a 12V electrical system, consistent with standard automotive low-voltage architecture.
The H11 at 55W draws significantly more power than the P21W at 21W, reflecting the functional difference between an illumination bulb intended to project light onto a road surface and a lower-power signalling bulb intended for visibility to other drivers.
Because both bulb types conform to ECE standards, replacement units sourced from international markets are electrically and physically compatible with the G550's fog light housings, provided the base type matches.
The front and rear fog light positions on the G550 use entirely different bulb families, H11 and P21W respectively, with no interchangeability between the two positions.