For the 2015 Audi A4, the listed low-beam and high-beam headlights both use D3S bulbs. The supplied fitment data does not identify separate projector or non-projector headlight variations, so verify the existing headlamp assembly before ordering.
Front turn signals use 64132 bulbs, while the reverse lights use 921 bulbs. The brake lights, center stop light, daytime running lights, parking lights, front and rear side markers, tail lights, rear turn signals, step lights, and license plate lights are listed as LED.
Interior fitment includes multiple listed options in several locations: dome lights use 6411 or 6428, while the glove box, interior, map, and trunk lights use 2825 or 98. Vanity lights use 6418. Because some interior positions have more than one listed bulb, compare the removed bulb or socket style before purchasing.