For the 2004 Mazda Mazda6, both the low-beam and high-beam headlights use H1 bulbs. The supplied fitment data does not identify a projector or non-projector headlight variation, so confirm the original bulb before ordering if your vehicle has replacement or aftermarket headlamp assemblies.
The front fog lights use H3 bulbs. Front turn signals use 2357A, while rear turn signals use 7440A. Brake and tail light applications use 7443R bulbs. The reverse lights take 921 bulbs.
Pay particular attention to the center stop light and parking lights, as each has two listed options. The center stop light may use 921 or 194, and the parking lights may use 2825 or 2357A. Compare the existing bulb with the original before purchasing. The license plate, front side marker, courtesy, dome, and map lights use 2825; the trunk light uses 2821.