Mack LEU Dome Light Bulb Size

The Mack LEU dome light bulb uses a 912 size specification for this component. The replacement chart covers vehicle production spanning 2011 to 2016.

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
2011-2016	912

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

The Mack LEU uses the 912 bulb for its dome light across the 2011-2016 model years.
The 912 is an ANSI-standardized bulb type, meaning its specifications are governed by a recognized North American standard applicable in both the US and Canada.
It belongs to the T15 form factor, which refers to a tubular bulb roughly 15/8 of an inch in width, fitted with a wedge-style base rather than a bayonet or screw mount.
The wedge base design means the bulb is held in place by the socket gripping the base directly, with no separate metal cap or pins involved.
The 912 operates at 12 volts and 12 watts, which is consistent with standard automotive electrical systems.
The 912 is a variant of the 921 bulb. While the two share the same T15 wedge form factor and voltage rating, they differ in wattage, as the 921 is rated at 18 watts versus the 912's 12 watts.
Because of the wattage difference, the 912 and 921 are not fully interchangeable in all applications, and substituting one for the other may affect brightness or circuit load.