The INFINITI QX56 tail light utilizes bulb sizes 12961 and 7440 and 3157 for the rear illumination system. Data for the specified components covers the range from 2004 through 2013.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The T10 wedge form factor is represented by two bulb sizes in the INFINITI QX56 inner tail light specifications: the 168 and the 12961. Both operate at 12V and share the same physical bulb shape, though they differ slightly in wattage, with the 168 rated at 4.9W and the 12961 rated at 5W.
The 168 is an ANSI-standardized designation used across the US and Canadian markets, while the 12961 is a Philips part number referencing the same T10 form factor with a W2.1x9.5d base. The W2.1x9.5d base specification defines the pin width and contact spacing of the wedge base, which determines physical socket compatibility.
For the 2013 INFINITI QX56, the inner tail light uses the 12961 only in vehicles produced up to September 2012. Units produced after that date use the 168 instead, meaning two different T10 bulbs apply to the same model year depending on production date.
The 7440 is a single-filament T20 wedge bulb rated at 12V and 21W. Its single filament means it serves one lighting function, as opposed to dual-filament bulbs that can serve two functions such as running light and brake light within a single housing.
The 3157 is a dual-filament T25 wedge bulb rated at 12V with a 27W high filament and a 7W low filament. The wattage difference between the two filaments allows the bulb to produce distinct brightness levels for separate functions within the same socket.
The inner tail light specification for the QX56 shows a transition from the dual-filament 3157 in 2004-2005 to the single-filament 7440 from 2006-2010, and then to T10 miniature wedge bulbs from 2011 onward. Each of these bulb types uses a different wedge base size and is not interchangeable with the others.
The 3157 and 7440 are both ANSI-standardized designations, meaning their electrical and physical characteristics conform to a defined industry standard rather than a manufacturer-specific specification.
The shift from the 7440 to the T10-based bulbs between the 2010 and 2011 model years represents a significant reduction in wattage for the inner tail light position, from 21W down to approximately 5W, which reflects a change in the optical or functional design of the tail light assembly.