When doing replacement or upgrading on 1997 – 2001 Cadillac Catera capsule halogen headlamps HID with, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

Low Beam Headlight 1997 – 1999 H7
High Beam Headlight 1997 – 1999 H7
Front Fog Light 1997 – 1999 H3-55W
Back Up Light 1997 – 1999 1156
Brake 1997 – 1999 1157
Dome Light 1997 – 1999 578
Front Side Marker 1997 – 1999 194
Front Turn Signal 1997 – 1999 3457
License Plate 1997 – 1999 12844
Parking Light 1997 – 1999 3457
Rear Side Marker 1997 – 1999 194
Rear Turn Signal 1997 – 1999 PY21W
Tail Light 1997 – 1999 1157
Courtesy 1997 – 1999 6411
Glove Box 1997 – 1999 578
Map Light 1997 – 1999 168
Low Beam Headlight 2000 – 2001 H7
High Beam Headlight 2000 – 2001 H7
Front Fog Light 2000 – 2001 H3-55W
Back Up Light 2000 – 2001 1156
Brake 2000 – 2001 1157
Dome Light 2000 – 2001 578
Front Side Marker 2000 – 2001 194
Front Turn Signal 2000 – 2001 3457
License Plate 2000 – 2001 12844
Parking Light 2000 – 2001 3457
Rear Side Marker 2000 – 2001 194
Rear Turn Signal 2000 – 2001 PY21W
Tail Light 2000 – 2001 1157
Courtesy 2000 – 2001 6411
Glove Box 2000 – 2001 578
Map Light 2000 – 2001 168
Low Beam Headlight 2000 – 2001 D2S
High Beam Headlight 2000 – 2001 H7
Front Fog Light 2000 – 2001 H3-55W
Back Up Light 2000 – 2001 1156
Brake 2000 – 2001 1157
Dome Light 2000 – 2001 6411
Front Side Marker 2000 – 2001 194
Front Turn Signal 2000 – 2001 3457
License Plate 2000 – 2001 12844
Parking Light 2000 – 2001 3457NA
Rear Side Marker 2000 – 2001 194
Rear Turn Signal 2000 – 2001 PY21W
Tail Light 2000 – 2001 1157
Courtesy 2000 – 2001 6411
Glove Box 2000 – 2001 578
Map Light 2000 – 2001 168