When doing replacement or upgrading on 2001 – 2005 Audi Allroad Quattro with capsule halogen headlamps HID, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

Low Beam Headlight 2001 – 2005 H1
High Beam Headlight 2001 – 2005 H9
Front Fog Light 2001 – 2005 H7
Back Up Light 2001 – 2005 1156
Brake 2001 – 2005 1157
Dome Light 2001 – 2005 6411
Front Side Marker 2001 – 2005 2357NA
License Plate 2001 – 2005 12844
Parking Light 2001 – 2005 2357
Rear Side Marker 2001 – 2005 1157
Rear Turn Signal 2001 – 2005 1156
Tail Light 2001 – 2005 1157
Front Inner Turn Signal 2001 – 2005 2357
Front Outer Turn Signal 2001 – 2005 12396NA
Engine Compartment Light 2001 – 2005 578
Glove Box 2001 – 2005 DE3423
Interior Door 2001 – 2005 194
Map Light 2005 12844
Stepwell 2001 – 2005 12844
Low Beam Headlight 2001 – 2005 D2S
High Beam Headlight 2001 – 2005 H9
Front Fog Light 2001 – 2005 H7
Back Up Light 2001 – 2005 1156
Brake 2001 – 2005 1157
Dome Light 2001 – 2005 6411
Front Side Marker 2001 – 2005 2357NA
License Plate 2001 – 2005 12844
Parking Light 2001 – 2005 2357
Rear Side Marker 2001 – 2005 1157
Rear Turn Signal 2001 – 2005 1156
Tail Light 2001 – 2005 1157
Front Inner Turn Signal 2001 – 2005 2357
Front Outer Turn Signal 2001 – 2005 12396NA
Engine Compartment Light 2001 – 2005 578
Glove Box 2001 – 2005 DE3423
Interior Door 2001 – 2005 194
Map Light 2005 12844
Stepwell 2001 – 2005 12844