Mercedes-Benz 450SEL Back Up Light Bulb Size

The Mercedes-Benz 450SEL back up light utilizes a P21W bulb size for illumination purposes. Available data for the specified component covers the period from 1973 through 1980.

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
1973-1980	P21W

Bulb Specifications

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

Other Locations

Additional Notes

The P21W is the sole back up light bulb type specified for the Mercedes-Benz 450SEL across all listed model years, covering 1973-1980.
The P21W is an ECE-standard single-filament bulb rated at 12 volts and 21 watts, designed for signalling applications.
P21W bulbs use a BA15s bayonet base, which is a single-contact bayonet fitting with a 15mm collar.
The BA15s base designation indicates a single-contact configuration, distinguishing it from the dual-contact BA15d variant, which is not interchangeable with this application.
The ECE designation on the P21W reflects compliance with United Nations Economic Commission for Europe lighting regulations, a standard widely adopted outside North America.
Because the P21W is an ECE-standard type rather than an SAE-standard type, substitution with North American market bulbs requires verification of base compatibility and wattage equivalence before fitment.