Harley-Davidson FLHRXS Road King Special Tail Light Bulb Size

Harley-Davidson FLHRXS Road King Special tail light requires a 3157 bulb size for replacement applications. The replacement chart covers 2017 to 2020 vehicle production years with corresponding bulb size specifications.

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
2017-2020	3157

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Dual-filament wedge bulb (T25). 12V, 27W/7W.	3157

Other Locations

Additional Notes

The 3157 is the sole tail light bulb type listed for the Harley-Davidson FLHRXS Road King Special across the 2017-2020 model years.
The 3157 is an ANSI-standardized bulb type recognized in both the United States and Canada, meaning it conforms to a defined set of electrical and physical parameters shared across manufacturers.
This bulb operates on a 12-volt system, which is standard for motorcycle electrical architectures of this type.
The 3157 carries a dual-filament design rated at 27W and 7W, where the higher wattage filament serves the brake light function and the lower wattage filament serves the running light function within a single housing.
The T25 designation refers to the bulb's wedge-base form factor, a classification that describes the physical base shape used to seat and retain the bulb within its socket.
Because the 3157 is a dual-filament type, substituting it with a single-filament equivalent such as the 3156 would result in the loss of either the running light or brake light function, making direct replacement with the correct type necessary for proper operation.