When doing replacement or upgrading on 1989 – 1994 Audi 100, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

High Beam and Low Beam Headlight1989 – 1994 9004
Front Fog Light1989 – 1994 H3-55W
Back Up Light1989 – 1994 1156
Brake1989 – 1994 1157
Dome Light1989 – 1994 578
Front Side Marker1989 – 1994 12821
Front Turn Signal1989 – 1994 P21/5W
License Plate1989 – 1994 T4W
Parking Light1989 – 1994 1157
Rear Side Marker1989 – 1994 12821
Rear Turn Signal1989 – 1994 1156
Tail Light1989 – 1994 1157
Center High Mount Stop Light1989 – 1994 12505
Courtesy1989 – 1994 12256
Engine Compartment Light1989 – 1994 578
Glove Box1989 – 1994 12929
Stepwell1989 – 1994 12844
Trunk1989 – 1994 6411