Mercedes-Benz GL320 front fog light uses H11 bulb size while rear fog light requires P21W bulb size. The replacement chart covers 2007 to 2009 production years with corresponding 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 GL320 uses two distinct bulb types across its fog light system: the H11 for front fog lights and the P21W for rear fog lights, both governed by ECE standards applicable in Europe and worldwide.
The H11 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PGJ19-2 base, and carries approval for use in the United States in addition to ECE-regulated markets.
The P21W is a single-filament signalling bulb operating at 12V and 21W, mounted via a BA15s bayonet base, a base type that requires a straight single-contact insertion rather than a screw or wedge fitting.
The GL320 front fog lights use the H11 across the 2007-2009 model years, indicating a consistent fitment specification throughout that production span.
The GL320 rear fog lights use the P21W across the 2007-2009 model years, maintaining the same signalling bulb specification across the same production span.
The H11 and P21W are not interchangeable with each other. Their base types, wattage ratings, and intended functions differ fundamentally, with the H11 serving an illumination role and the P21W serving a signalling role.
The PGJ19-2 base of the H11 is a keyed connector specific to that bulb family, meaning physically similar halogen bulbs with different base designations, such as H8 or H9, would not seat correctly in an H11 socket despite sharing the same general form.
The BA15s bayonet base of the P21W denotes a single-contact fitting with a 15mm barrel width, distinguishing it from the BA15d, which carries two contacts. Substituting a dual-contact bulb in a single-contact socket would result in incorrect fitment.
At 21W, the P21W draws considerably less power than the 55W H11, reflecting the lower energy demands of a signalling function compared to a forward-facing fog illumination function.
Both bulb types operate on a 12V electrical system, consistent with standard automotive low-voltage architecture used across passenger vehicles of this class.