Mack MRU Dome Light Bulb Size

The Mack MRU dome light bulb uses a 912 size specification for this interior lighting component. The replacement chart covers vehicle production spanning 2011 to 2017 with corresponding bulb size data.

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
2011-2017	912

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). Variant of 921. 12V, 12W.	912

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Additional Notes

The 912 bulb is the sole dome light bulb size specified for the Mack MRU across the 2011-2017 model years.
The 912 is an ANSI-standardized bulb type, meaning it conforms to a defined set of electrical and physical specifications recognized across the United States and Canada.
It belongs to the T15 wedge bulb family, a form factor characterized by a wedge-shaped base that seats directly into a socket without a separate metal cap or pins.
The 912 operates at 12 volts and draws 12 watts, which is consistent with standard low-voltage automotive electrical systems.
The 912 is a variant of the 921 bulb. While both share the T15 wedge form factor and 12-volt rating, the 921 is rated at 18 watts, making the two types electrically distinct despite their physical similarities.
Because of the wattage difference between the 912 and 921, substituting one for the other may affect circuit load and light output, even though the physical base may allow fitment in the same socket.