For the 2005 Audi TT, low-beam fitment depends on the headlight type. Models with halogen headlights use an H1 bulb, while models equipped with HID headlights use a D2S bulb. No high-beam bulb fitment is listed in the supplied data, so verify the headlamp assembly before ordering.
Fog-light fitment is listed as either H3 or H3C, indicating another configuration-dependent application to check against the existing bulb and housing. Other notable exterior bulbs include 64136 for the front turn signal, 7506 for the rear turn signal and reverse light, and 7528 for both the brake and tail lights. The center stop light is LED.
For smaller lighting applications, the license-plate and courtesy lights use 6418, while the parking and front side-marker lights use 64132. Rear side-marker and trunk-light fitment may be 2825 or 98. Interior dome-light fitment is listed as 6411 or 6428, with 2821 for the glove-box light and 64111 for the map light. Confirm the installed configuration when multiple sizes are shown.