Mercedes-Benz G550 4x4 front side marker uses a 3893 bulb size and rear side marker uses a 12821 bulb size. The replacement chart covers 2017 to 2018 vehicle production years with bulb size 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 4x4 uses two distinct bulb types across its side marker positions for the 2017-2018 model years: the 3893 at the front and the 12821 at the rear.
The 3893 is an ANSI-standardized bulb recognized in both the United States and Canada, operating on a 12V system with a BAY15d bayonet base.
A BAY15d base is a dual-contact bayonet fitting with offset pins, which physically prevents incorrect single-filament bulbs from being seated in its place.
The 3893 carries a dual-filament design, meaning it houses two separate filaments within a single envelope, each serving a distinct lighting function.
The 12821 is a Philips part number designation for a miniature wedge-style bulb, rated at 12V and 5W, with a W2.1x9.5d wedge base.
The T10 form factor of the 12821 refers to a tubular bulb body approximately 10mm wide, a common sizing convention in miniature automotive lighting.
The W2.1x9.5d base of the 12821 is a wedge-type fitting held in place by tension rather than a locking mechanism, which distinguishes it from the bayonet retention system used by the 3893.
Because the front and rear side markers use fundamentally different base types, the 3893 and 12821 are not interchangeable with each other.