Mack DMM License Plate Bulb Size

The Mack DMM license plate light requires a single 1891 bulb size for the exterior lighting system on the rear of the vehicle. Available data covers the range from 1981 to 1997 for the specified component.

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 Type	Shop
1981-1997	1891	Check Price

Bulb Specifications

Description	Type	Shop
ANSI standard (US & Canada). Miniature wedge bulb (T5). 12V, 2W.	1891	Check Price

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Additional Notes

The Mack DMM uses the 1891 bulb size for the license plate position across all listed model years, spanning 1981-1997.
The 1891 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical specifications shared across those markets.
The 1891 belongs to the T5 form factor, which refers to a tubular bulb with a width of 5/8 of an inch. It uses a miniature wedge base, a baseless design where the glass envelope itself is pinched and inserted directly into the socket.
The 1891 operates at 12 volts and draws 2 watts, placing it among the lower-wattage bulbs used in automotive applications. This output level is typical for illumination tasks that require visibility rather than high brightness, such as license plate lighting.
Because the 1891 uses a wedge base rather than a bayonet or screw base, substitution with bulbs of a different base type is not compatible, even if voltage and wattage ratings are otherwise similar.