International 8500 TranStar Turn Signal Bulb Size

Additional Notes

• The International 8500 TranStar front turn signal uses the 3157NA bulb across the 2008-2011 model years.
• The 3157NA is an ANSI-standardized bulb type, meaning its physical and electrical specifications conform to a defined North American standard recognized in both the United States and Canada.
• This bulb carries a dual-filament design, with one filament rated at 27 watts and the other at 7 watts. In automotive applications, the higher-wattage filament typically serves the turn signal or brake function, while the lower-wattage filament serves a parking or running light function.
• The 3157NA belongs to the T25 wedge bulb family. The wedge base design means the bulb is held in its socket by the tension of the base itself rather than by a separate bayonet or screw mechanism.
• The "NA" suffix in the 3157NA designation indicates natural amber glass. The glass envelope is tinted amber at the factory, which produces the amber signal color without relying solely on a colored lens.
• The bulb operates on a 12-volt electrical system, consistent with standard automotive DC voltage found in most commercial and passenger vehicles.
• The 3157NA is closely related to the 3157 bulb, which shares the same base and filament configuration but uses clear glass. The two types are not always interchangeable in applications where the lens is clear, since the amber tint is built into the 3157NA glass rather than the housing.