The Mercedes-Benz 560SEC brake component requires a P21W bulb size for proper operation and visibility on the road. Available data for the specified vehicle covers the range from 1986 through 1991.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Mercedes-Benz 560SEC uses the P21W bulb type across all brake light positions for the 1986-1991 model years.
The P21W is an ECE-standardized single-filament bulb rated at 12 volts and 21 watts, designed primarily for signalling applications such as brake and stop lights.
P21W bulbs use a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar. The "s" designation indicates a single contact pin, distinguishing it from dual-contact variants.
The BA15s base is not interchangeable with the BA15d base. The BA15d carries two contact pins for dual-filament operation, and substituting one for the other is not compatible with the 560SEC's brake light circuit.
Both the standard brake lights and the Center High Mount Stop Light on the 560SEC share the same P21W specification across the full 1986-1991 production run.
The P21W designation follows ECE (Economic Commission for Europe) regulations, meaning the bulb meets internationally recognized performance and safety standards used outside North America as well as in European markets.
Because the P21W is a single-filament bulb, it serves one dedicated function per socket. It does not combine brake and tail light functions within a single bulb, unlike dual-filament types such as the P21/5W.
The 21-watt output of the P21W produces a relatively high light intensity for a single-filament signal bulb, which is a characteristic suited to stop light applications where visibility is a safety requirement.