Mercedes-Benz 450SE Back Up Light Bulb Size

The Mercedes-Benz 450SE back up light requires a P21W bulb size for the specific lighting component located at the rear of the vehicle. Data for the bulb specifications covers the range from 1973 to 1976.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1973-1976	P21W

Bulb Specifications

Description	Bulb Size
ECE standard (Europe & worldwide). Single-filament signalling bulb with BA15s bayonet base. 12V, 21W.	P21W

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Additional Notes

The Mercedes-Benz 450SE uses the P21W bulb for its back up light across the 1973-1976 model years.
The P21W is an ECE-standard bulb, meaning it conforms to the United Nations Economic Commission for Europe regulations, which govern automotive lighting across European and many worldwide markets.
As a single-filament bulb, the P21W is dedicated to one lighting function, which in this application is the back up light.
The P21W operates at 12 volts and consumes 21 watts, placing it in the standard range for automotive signalling and reversing lamps.
The P21W uses a BA15s bayonet base, where "BA15" refers to the 15mm bayonet cap and "s" denotes a single contact at the base, distinguishing it from dual-contact variants such as the BA15d.
The BA15s single-contact base is not interchangeable with the BA15d base. Substituting a dual-contact bulb in a single-contact socket would result in incorrect fitment.