The Jaguar XKR tail light utilizes a P21/5W bulb size for the rear illumination system. Available information covers the span of time from 2000 through 2015 for the specified vehicle.
The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.
The Jaguar XKR outer tail light position uses the P21/5W bulb across all model years from 2000 to 2015.
The P21/5W is an ECE-standard dual-filament bulb rated at 12V with a 21W main filament and a 5W secondary filament, mounted on a BAY15d offset bayonet base.
The BAY15d base features two pins at different heights, a design that prevents incorrect single-filament bulbs from being seated in a dual-filament socket.
The inner tail light position on the Jaguar XKR applies only to the 2007-2009 model years, where it uses the 12961 bulb size.
The 12961 is a Philips part number designating a T10 miniature wedge bulb with a W2.1x9.5d base, rated at 12V and 5W.
The T10 wedge base of the 12961 is not compatible with the BAY15d bayonet socket used by the P21/5W, making the two bulb types non-interchangeable despite both operating at 12V.
The wattage difference between the two bulb types is significant: the 12961 draws 5W on a single filament, while the P21/5W draws up to 21W on its primary filament, reflecting their different functional roles within the tail light assembly.
The P21/5W designation follows ECE (Economic Commission for Europe) naming conventions, where "P" denotes a prefocus-style lamp, "21" refers to the higher wattage filament, and "5W" refers to the lower wattage filament.