Buick Regal TourX Back Up Light Bulb Size

The Buick Regal TourX back up light requires a bulb size of 921 for the specific lighting component located at the rear of the vehicle. Data for the bulb size covers the range from 2018 to 2020.

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
2018-2020	921

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Wedge bulb (T15). 12V, 16W.	921

Other Locations

Additional Notes

The 921 bulb is the specified back up light bulb for the Buick Regal TourX across the 2018-2020 model years.
The 921 is classified as a wedge-type bulb, meaning it uses a plastic wedge base rather than a metal pin or bayonet fitting, and seats directly into a matching socket without a separate holder.
The T15 designation refers to the bulb's tubular shape, with the numeric portion indicating a width of 15 eighths of an inch across the envelope.
The 921 operates at 12 volts and draws 16 watts, which is consistent with standard automotive reverse light applications.
The 921 follows the ANSI standardization system, meaning its physical and electrical characteristics are defined by a recognized industry specification applicable in both the United States and Canada.
Because the 921 is an ANSI-standardized wedge bulb, direct-fit LED replacements marketed under the T15 or 921 designation are generally socket-compatible, though electrical behavior such as load resistance may differ from the original halogen unit.