The Mercedes-Benz CL600 brake light requires a P21/4W bulb size for proper installation and function. Data for the specific component covers the range from 1998 to 1999.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz CL600 uses two distinct bulb types across its brake lighting system for the 1998-1999 model years: the P21/4W for standard brake lights and the H21W for the center high mount stop light.
The P21/4W is a dual-filament bulb operating at 12V with a 21W/4W output rating, meaning it draws 21 watts on the brake filament and 4 watts on the secondary filament, which is typically used for a combined tail and brake light function.
The P21/4W uses a BAZ15d bayonet base, an offset-pin bayonet fitting designed to prevent incorrect bulb insertion by ensuring only one rotational orientation is possible during installation.
The H21W is a single-filament bulb rated at 12V and 21W, dedicated solely to the stop light function in the center high mount position, with no secondary filament for auxiliary lighting duties.
The H21W uses a BAY9s base, a bayonet-style fitting with offset pins that is physically incompatible with the BAZ15d base of the P21/4W, making the two bulb types non-interchangeable despite sharing the same 21W power rating.
Both the P21/4W and H21W conform to ECE standards, a regulatory framework recognized across Europe and numerous other markets worldwide, governing performance and dimensional requirements for automotive signalling bulbs.
Because the P21/4W and H21W differ in both base type and filament configuration, substituting one for the other in the CL600 is not possible without a socket adapter, and even then the filament configuration would not match the intended circuit design.