Rolls-Royce Silver Shadow Map Light Bulb Size

The Rolls-Royce Silver Shadow map light requires a 257 bulb size for the interior lighting system. Data for the specific component covers the period from 1973 through 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	257

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon or BA9s base instrument bulb. 12V, 2W.	257

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Additional Notes

The Rolls-Royce Silver Shadow uses the 257 bulb for its map light across the 1973-1976 model years.
The 257 is an ANSI-standardized bulb, meaning its specifications are governed by a recognized North American standard used in both the United States and Canada.
This bulb operates at 12 volts and draws 2 watts, placing it in the low-wattage range typical of interior courtesy and reading applications.
The 257 is available in either a festoon or BA9s base configuration, and these two base types are not interchangeable with each other despite sharing the same bulb designation number.
A festoon bulb is cylindrical in shape and is held in place by contact at each end, while a BA9s is a single-contact bayonet cap base, so the correct base type for the specific Silver Shadow lamp housing must be confirmed before replacement.