Mercury Monarch Dome Light Bulb Size

The Mercury Monarch dome light requires a 211-2 or 561 bulb size depending on the specific production period. Data for the lighting components covers the range from 1975 to 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
1977-1980	211-2
1976	561
1975	211-2

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 41mm length, SV8.5 base. 12V, 12W.	211-2
ANSI standard (US & Canada). Festoon bulb, 44mm length, end-cap contacts. 12V, 12W.	561

Other Locations

Additional Notes

The Mercury Monarch dome light uses two festoon bulb types across its production years: the 211-2 and the 561, both rated at 12V and 12W.
Festoon bulbs are cylindrical lamps that mount horizontally between two contact points, a common format for dome light applications in automotive interiors.
The 211-2 is the dominant fitment for the Mercury Monarch dome light, appearing in the 1975 and 1977-1980 model years.
The 211-2 measures 41mm in length and uses an SV8.5 base, which features a single central contact pin on each end seated within a plastic or metal cap.
The 561 is specified exclusively for the 1976 Mercury Monarch and measures 44mm in length, making it 3mm longer than the 211-2.
The 561 uses end-cap contacts rather than an SV8.5 base, meaning electrical contact is made through metal caps at each end of the bulb rather than through a central pin.
Despite sharing identical voltage and wattage ratings, the 211-2 and 561 are not interchangeable due to their differing lengths and contact types.
Both bulb types conform to ANSI standards applicable in the United States and Canada, indicating standardized physical and electrical tolerances.