The Mercedes-Benz ML350 tail light utilizes P21W and P21/4W bulb sizes depending on the specific version required for the lighting assembly. Data for the provided specifications covers the range from 2003 through 2011.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The two bulb types present across these specifications are the P21W and the P21/4W, both governed by ECE standards used in Europe and worldwide markets.
The P21W is a single-filament signalling bulb operating at 12V and 21W, fitted with a BA15s bayonet base.
The P21/4W is a dual-filament signalling bulb operating at 12V with filaments rated at 21W and 4W respectively, fitted with a BAZ15d bayonet base.
The BA15s and BAZ15d bases are physically distinct, meaning P21W and P21/4W bulbs are not interchangeable despite sharing a similar appearance and voltage rating.
For the Mercedes-Benz ML350, the outer tail light on 2006-2008 models takes a P21W bulb, while 2003-2005 models take a P21/4W bulb.
A second set of outer tail light positions shows a split at a different year: 2008-2011 models use the P21W, while 2003-2007 models use the P21/4W.
The year 2008 is associated with the P21W across both outer tail light position sets, indicating consistent fitment for that model year regardless of position group.
The dual-filament P21/4W serves two brightness levels within a single bulb housing, a function the single-filament P21W does not replicate, which reinforces why substitution between the two types would affect lighting performance.