Mercedes-Benz GL350 front fog light uses H11 bulb size while rear fog light requires H21W bulb size. The replacement chart covers 2010 to 2016 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 H11 and H21W are the two bulb types specified for the Mercedes-Benz GL350's fog light system, each serving a distinct position within the vehicle.
The H11 is a single-filament halogen bulb operating at 12V and 55W, built to the ECE standard and also approved for use in the United States. It uses a PGJ19-2 base, which is a locating-pin style connector that physically prevents incorrect installation of incompatible bulbs.
The H21W is a single-filament signalling bulb rated at 12V and 21W, also conforming to the ECE standard. Its lower wattage reflects its role as a signalling light rather than an illumination source. It uses a BAY9s base, a bayonet-style fitting with offset pins that enforce correct polarity orientation during installation.
The PGJ19-2 base of the H11 and the BAY9s base of the H21W are not interchangeable. The two bulb types are mechanically incompatible with each other's housings by design.
For the Mercedes-Benz GL350, the front fog light position uses the H11 bulb for the 2010-2011 model years.
The rear fog light position uses the H21W bulb across the 2010-2016 model years.
The H21W's BAY9s base features asymmetrically positioned bayonet pins, which means the bulb can only be seated in one orientation within its socket, reducing the risk of reverse-polarity installation.
The H11's PGJ19-2 base is part of the PGJ19 family, which includes several visually similar variants. Substituting a different member of that family, such as the H8 or H9, would result in a wattage mismatch even if physical fitment were possible.