Mercedes-Benz ML450 front fog light uses H11 bulb size while rear fog light requires 921 bulb size. Replacement chart covers 2010 to 2011 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 ML450 uses two distinct bulb types across its fog light positions: the H11 for front fog lights and the 921 for rear fog lights, covering the 2010-2011 model years.
The H11 is a single-filament halogen bulb operating at 12V and 55W, built to the ECE standard used in Europe and worldwide, with approval also extended to the US market.
The H11 uses a PGJ19-2 base, a locking bayonet-style connector that is specific to the H11 family and is not interchangeable with other common halogen bases such as the H9 or H8, despite those bulbs sharing a physically similar housing profile.
The 921 is a wedge-type bulb classified under the T15 form factor, operating at 12V and 16W, and is governed by the ANSI standard applicable in the US and Canada.
The significantly lower wattage of the 921 (16W) compared to the H11 (55W) reflects the functional difference between a rear fog light, which serves as a visibility signal, and a front fog light, which is designed to illuminate road surfaces in low-visibility conditions.
The wedge base of the 921 relies on tension from its wire leads to hold it in the socket, with no separate locking mechanism, which distinguishes it from the PGJ19-2 base of the H11.
The H11 and 921 are not interchangeable with each other due to differences in base type, wattage, and intended light output, and substituting one for the other in the ML450 would result in an incompatible fit.
The 921 bulb shares its T15 wedge form factor with several other ANSI-coded bulbs, but wattage and voltage ratings must match the original specification to ensure proper circuit load and light output in the rear fog position.