Subaru WRX STI front and rear side marker bulbs use 12961 and 168 bulb sizes across both locations. The replacement chart covers 2015 through 2020 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.
The Subaru WRX STI uses two distinct bulb types across its front and rear side marker positions: the 168 and the 12961. Both are T10 miniature wedge bulbs operating at 12 volts, placing them in the same general bulb family despite carrying different part designations.
The 168 is an ANSI-standardized bulb recognized across the United States and Canada. It carries a rated output of 4.9 watts and fits a standard T10 wedge base.
The 12961 is a Philips part number rather than an ANSI designation. It is also a T10 wedge bulb but specifies a W2.1x9.5d base and is rated at 5 watts on a 12-volt circuit.
The W2.1x9.5d base designation on the 12961 describes a wedge-type base with a 2.1mm wire contact width and a 9.5mm insertion depth, which is the standardized IEC format for describing this base type.
For the Subaru WRX STI (2015-2019), both the front and rear side marker positions use the 168 bulb.
The 2020 Subaru WRX STI shifted to the 12961 bulb in both the front and rear side marker positions, replacing the 168 used in prior model years.
Although the 168 and 12961 are both T10 wedge bulbs with nearly identical wattage ratings, they carry separate part designations and the 12961 is defined under a manufacturer-specific numbering system rather than a shared industry standard.
The front and rear side marker positions mirror each other exactly across all model years in the specifications, with each position using the same bulb size as the other for any given year.