For the 2001 Porsche 911, the supplied fitment data lists a D2S bulb for the low-beam headlight. No high-beam bulb is listed, so verify the original bulb before ordering a replacement for that position.
Other useful exterior fitments include 7506 for the front turn signal and reverse light, 7507 for the rear turn signal, and 7528 for the brake and tail lights. The center stop light uses 2821, while the license-plate light uses 6418.
Parking, front side-marker, and courtesy lighting may use either 2825 or 98. Interior applications also vary by location: dome, engine, and trunk lights use either 6411 or 6428, the glove-box light uses 6428, and the map light uses 2886X. For instrument lighting, compare the original bulb because the data lists either 2351MFX6 or 2821.