Subaru WRX STI front and rear turn signal bulbs use 7440NA size replacement bulbs. The chart covers 2015 to 2020 model years with bulb size specifications.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The 7440NA is the sole turn signal bulb type specified for the Subaru WRX STI across all listed model years, applying to both the front and rear turn signal positions.
The 7440NA bulb follows the T20 wedge form factor, a single-filament design that fits into a wedge-style socket without a separate base or pins.
All front and rear turn signal positions on the WRX STI (2015-2020) share the same 7440NA specification, meaning the front and rear sockets accept the same bulb.
The "NA" suffix in 7440NA denotes natural amber glass, which means the amber color is produced by the glass envelope itself rather than by an amber-tinted lens or housing.
The 7440NA operates at 12 volts and draws 21 watts, which is the standard wattage for single-filament automotive turn signal bulbs in this class.
The 7440NA carries ANSI standardization recognized in the United States and Canada, placing it within a regulated performance and dimensional framework for those markets.
Because the 7440NA uses a single filament, it serves a dedicated turn signal function and is not a dual-purpose bulb combining turn signal and brake or running light duties.
The standard 7440 and the 7440NA share the same T20 wedge base and electrical ratings, but substituting a clear 7440 for the 7440NA in an amber-lens housing would produce a different light output color than the factory-specified natural amber.