Mercedes-Benz GLA45 AMG front fog lights use H11 bulbs and rear fog lights use H21W bulbs for replacement. The chart contains bulb size specifications covering 2015 to 2019 vehicle production years.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz GLA45 AMG uses the H11 bulb for the front fog light position across the 2015-2019 model years.
The H11 is a single-filament halogen bulb operating at 12V and 55W, fitted with a PGJ19-2 base, and is rated under the ECE standard, which governs lighting equipment across Europe and much of the world.
The H11 also carries approval for use in the United States, making it one of the few ECE-standard bulbs with dual-market regulatory acceptance.
The rear fog light position on the GLA45 AMG uses the H21W bulb across the same 2015-2019 model years.
The H21W is a single-filament signalling bulb rated at 12V and 21W, fitted with a BAY9s base, and is also governed by the ECE standard.
The BAY9s base on the H21W is an offset bayonet fitting, which is physically distinct from the PGJ19-2 base of the H11, making the two bulbs non-interchangeable despite both operating on 12V systems.
The wattage difference between the H11 at 55W and the H21W at 21W reflects their respective roles, with the higher-wattage H11 serving an illumination function and the lower-wattage H21W serving a signalling function.
Because the H11 uses a wedge-style locking collar base rather than a bayonet mount, installation and removal procedures differ between the front and rear fog light positions on this vehicle.