The Mercedes-Benz CL500 tail light utilizes 12821 and P21/4W bulb sizes depending on the specific production period. Available data covers the range from 1998 through 2006.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CL500 outer tail light uses two distinct bulb types across its model years: the P21/4W and the T10 wedge format, represented by Philips part numbers 12961 and 12821.
The P21/4W is an ECE-standard dual-filament signalling bulb rated at 12V with a 21W main filament and a 4W secondary filament, mounted on a BAZ15d bayonet base. The dual-filament design allows a single bulb to serve two lighting functions simultaneously.
The BAZ15d bayonet base on the P21/4W is an offset pin design, meaning the two pins are positioned at different heights around the base. This prevents incorrect insertion and ensures the filaments align with their intended circuits.
The CL500 outer tail light used the P21/4W across the 1998-2004 model years.
For the 2005-2006 model years, the outer tail light specification shifted to the Philips 12821, a T10 miniature wedge bulb rated at 12V and 5W with a W2.1x9.5d base.
The 1998-1999 model years carry a dual listing for the outer tail light, specifying both the P21/4W and the Philips 12961. The 12961 is also a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W.
The Philips 12961 and 12821 share identical electrical ratings and base types, both being 12V, 5W T10 wedge bulbs with W2.1x9.5d bases. They are differentiated by Philips part number rather than by electrical or physical specification.
The P21/4W and the T10 wedge bulbs are not interchangeable. They differ in base type, wattage, filament count, and physical form, making cross-substitution between these two types incompatible with the intended socket.