The Jaguar XK tail light requires a P21/5W bulb size for proper installation and function within the rear lighting assembly. Available data covers the specific range from 2007 to 2015.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The P21/5W is the most widely used bulb type across the Jaguar XK tail light specifications, appearing in the outer tail light position across all documented model years from 2007-2015.
The P21/5W follows the ECE standard, which is a European and internationally recognized lighting regulation framework, and it uses a BAY15d bayonet base with dual-filament operation rated at 12V and 21W/5W.
The dual-filament design of the P21/5W allows a single bulb to serve two functions within the outer tail light assembly, with the 21W filament typically handling stop or turn signal duties and the 5W filament handling the running light function.
The BAY15d bayonet base on the P21/5W features offset pins, which physically prevents incorrect installation of a single-filament bulb in a socket designed for dual-filament operation.
The inner tail light position on the Jaguar XK (2007-2009) uses the 12961, a Philips-designated miniature wedge bulb of the T10 type with a W2.1x9.5d base, rated at 12V and 5W.
The W2.1x9.5d base on the 12961 bulb is a wedge-style fitting, meaning it is held in place by the socket's contact tension rather than a locking or bayonet mechanism.
The 12961 and P21/5W are not interchangeable, as they differ in base type, wattage, filament count, and physical form factor.
The inner and outer tail light positions on the Jaguar XK require different bulb types, meaning the two assemblies draw from separate and incompatible bulb specifications.