The Mercedes-Benz GLS550 high beam and low beam headlight bulbs utilize D1S and H7 size specifications for optimal illumination performance. The replacement chart covers 2017 through 2019 model years with corresponding bulb size data.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz GLS550 headlight specifications for 2017-2019 list two distinct headlamp system types: HID (High-Intensity Discharge) and halogen capsule. Each system uses a different bulb type for both high and low beam functions, meaning the correct bulb depends entirely on which headlamp system is installed on the vehicle.
The D1S is an HID xenon discharge bulb operating at 85V and 35W. Unlike halogen bulbs, it produces light through an electrical arc between tungsten electrodes within a xenon gas-filled quartz capsule, rather than through filament combustion. It uses a PK32d-2 base and includes an integral ignitor as part of the bulb assembly.
The D1S is designed exclusively for projector-type housings. Installing it in a reflector-style housing would produce improper light distribution, making housing compatibility a critical factor beyond the base type alone.
The H7 is a single-filament halogen bulb rated at 12V and 55W, fitted with a PX26d base. It carries ECE approval for use in Europe and worldwide markets, and is also approved for use in the United States and Japan, giving it broad regulatory acceptance across major automotive markets.
Both the D1S and H7 are governed by ECE (Economic Commission for Europe) standards, which define performance, photometric output, and dimensional tolerances. Bulbs carrying ECE certification are required to meet these standardized parameters regardless of manufacturer.
The D1S and H7 use physically incompatible bases, PK32d-2 and PX26d respectively, so they are not interchangeable with each other under any circumstance. Substituting one for the other is not mechanically possible without modifying the headlamp housing.
The same bulb sizes apply to both the high beam and low beam positions across the 2017-2019 model years. On GLS550 vehicles equipped with HID headlamps, the D1S serves both functions, while on halogen capsule-equipped vehicles, the H7 serves both functions.
Because the GLS550 was offered with two different headlamp systems during the 2017-2019 period, confirming the installed headlamp type before sourcing a replacement bulb is a necessary step, as the vehicle model year alone does not determine the correct bulb size.