The Mercedes-Benz E55 AMG tail light utilizes 12821 and P21/4W bulb sizes for the rear lighting system. Data for the specified components covers the range from 1999 through 2003.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21/4W is an ECE-standard dual-filament bulb rated at 12V with a 21W main filament and a 4W secondary filament, mounted on a BAZ15d bayonet base. The two filaments allow a single bulb to serve two lighting functions simultaneously, such as combined tail and brake light duties.
The Mercedes-Benz E55 AMG outer tail light uses the P21/4W for model years 2000-2002, making it the most frequently specified bulb across the listed positions and years in these specifications.
The BAZ15d bayonet base on the P21/4W is an offset twin-contact design. The asymmetric pin placement prevents incorrect installation, ensuring the higher-wattage filament is always connected to the intended circuit.
Bulbs 12961 and 12821 are both Philips part numbers for T10 miniature wedge bulbs sharing identical electrical ratings of 12V and 5W, and both use the W2.1x9.5d wedge base.
Despite their shared physical and electrical characteristics, 12961 and 12821 are distinct Philips catalog entries and are not listed interchangeably within the same model year position in these specifications.
The 1999 E55 AMG outer tail light carries two separate bulb entries: the 12961 in one position and the 12821 in another, indicating the two positions on that year's assembly require different catalog references despite the bulbs being electrically equivalent.
The W2.1x9.5d wedge base on the T10 bulbs is a capless design where the glass envelope itself forms the contact points. This base type is not compatible with bayonet or screw-type sockets.
A P21/4W bulb cannot substitute for a T10 wedge bulb in these specifications. The BAZ15d bayonet base and the W2.1x9.5d wedge base are physically incompatible socket types, and the wattage ratings differ substantially.
The 2003 E55 AMG outer tail light specifies the 12821, while the 2000-2002 years list the P21/4W for the same outer tail light position, indicating a change in bulb type across the production run.
The T10 designation on the 12961 and 12821 refers to a tubular bulb with a width of approximately 10 millimeters, a standard sizing classification used across many automotive interior and exterior lighting applications.