Mack Granite (GU) Roof Marker Bulb Size

The Mack Granite (GU) roof marker bulb uses a 168 size bulb for this component. The replacement chart covers vehicle production years spanning 2011 to 2022.

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
2011-2022	168

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Miniature wedge bulb (T10). 12V, 4.9W.	168

Other Locations

Additional Notes

The Mack Granite (GU) uses the 168 bulb size for the roof marker position across the 2011-2022 model years.
The 168 bulb is classified as a miniature wedge type, designated by the T10 envelope shape, which refers to a tubular glass form measuring 10/8 of an inch in width.
The 168 bulb operates at 12 volts and draws 4.9 watts, placing it in the low-wattage range typical of marker and clearance lighting applications.
The 168 is an ANSI-standardized bulb recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical tolerances shared across manufacturers.
The wedge base design of the 168 bulb means it is held in its socket by the tension of the base contacts rather than by a bayonet or screw mechanism, which is a common trait in marker light applications on commercial vehicles.
Because the same bulb number applies uniformly across all listed model years, there are no fitment variations within the 2011-2022 range for this position.
The T10 wedge form factor is shared by several bulb numbers in the miniature wedge family, so wattage and voltage ratings should be confirmed before substituting an alternative bulb, as physical fit alone does not guarantee electrical compatibility.