Mini Cooper Tail Light Bulb Size

Additional Notes

• The P21W bulb is a single-filament signalling bulb operating at 12V and 21W, built to ECE standards and fitted with a BA15s bayonet base. It is used across the Mini Cooper for model years 2007-2024.
• The P21/5W is a dual-filament signalling bulb rated at 12V with filaments at 21W and 5W. It uses a BAY15d bayonet base and follows the same ECE standard. It appears in the Mini Cooper for model years 2002-2006.
• The BA15s base on the P21W has a single contact pin, while the BAY15d base on the P21/5W has two offset pins. These two bases are not interchangeable, which means the P21W and P21/5W cannot substitute for one another despite sharing the same 21W primary filament rating.
• The dual-filament design of the P21/5W allows it to serve two lighting functions within a single bulb housing, with the 5W filament typically handling a secondary function such as parking or running light duty alongside the main 21W filament.
• Both bulb types conform to ECE regulations, which are the prevailing standards in Europe and many markets worldwide. This regulatory basis governs the photometric and electrical performance requirements each bulb must meet.
• For the Mini Cooper (2014-2024), the P21W specification carries a "without LED taillights" condition, indicating that this bulb size applies only to vehicles not equipped with factory LED taillight assemblies.
• The same "without LED taillights" condition is noted for the 2015-2013 boundary year of 2014, making 2014 the earliest model year in the specifications where this fitment condition is recorded alongside the P21W designation.
• Model years 2007-2013 list the P21W without any fitment condition attached, suggesting the LED taillight variant distinction was not a factor recorded for those years in these specifications.