The Audi A8 inner tail light uses a 12821 bulb size, the outer tail light uses a P21/5W bulb size, and the tail light uses a 1034 bulb size. The replacement chart covers vehicle production years from 1997 to 2003 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 Audi A8 inner tail light position uses the 12821 bulb across the 1997-2003 model years.
The 12821 is a Philips part number designating a miniature wedge-style T10 bulb with a W2.1x9.5d base, rated at 12V and 5W. Its single-filament, low-wattage output is typical for indicator or marker lighting roles.
The Audi A8 outer tail light position uses the P21/5W bulb across the 1997-2003 model years.
The P21/5W is an ECE-standard dual-filament bulb with a BAY15d bayonet base, rated at 12V with filaments drawing 21W and 5W respectively. The dual-filament design allows a single bulb to serve two lighting functions, such as tail and brake light, within one housing.
The outer tail light position on the Audi A8 also lists the 1034 bulb for the 2000-2003 model years.
The 1034 is an ANSI-standard dual-filament bulb sharing the BAY15d bayonet base and a 12V, 21W/5W rating with the P21/5W. It is classified as a variant of the 1157 and follows North American standardization rather than the ECE framework used by the P21/5W.
Although the P21/5W and the 1034 share the same BAY15d base type and equivalent wattage ratings, they originate from different standardization systems. The BAY15d base features offset pins that prevent incorrect single-filament bulbs from being seated in a dual-filament socket.
The presence of both P21/5W and 1034 listings for the outer tail light on the 2000-2003 Audi A8 reflects regional fitment differences, with the P21/5W associated with European and international markets and the 1034 associated with North American markets.