Rolls-Royce Silver Wraith II Map Light Bulb Size

The Rolls-Royce Silver Wraith II map light requires bulb size 257 or 57 depending on the specific application. Data for the bulb sizes covers the range from 1977 to 1979.

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
1978-1979	257
1977	57

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon or BA9s base instrument bulb. 12V, 2W.	257
ANSI standard (US & Canada). Single-filament bulb with BA9s base. 12V, 1W.	57

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Additional Notes

The Rolls-Royce Silver Wraith II uses two distinct bulb types across its map light specifications: the 257 and the 57, both classified under ANSI standards applicable to the US and Canadian markets.
The 257 bulb operates at 12 volts and draws 2 watts, fitting either a festoon or BA9s base configuration, which means it can be seated in two physically different socket types depending on the application.
The 57 bulb is a single-filament type with a BA9s base, operating at 12 volts and drawing 1 watt, making it the lower-wattage option of the two bulbs listed.
The 1977 Silver Wraith II map light takes the 57 bulb, while the 1978-1979 model years take the 257 bulb, indicating a specification change occurred between the 1977 and 1978 model years.
Although both the 257 and the 57 share the BA9s base type, their wattage ratings differ, and the 257 also supports a festoon base alternative, so the two bulbs are not directly interchangeable without confirming the socket type and wattage tolerance of the fixture.