When doing replacement or upgrading on 1973 – 2017 Buick Regal Somerset Coupe Sedan 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 1988 – 1990, 1997 – 2004 9006
1976 – 1977, 1981 – 1987 H4656
High Beam Headlight 1988 – 1990, 1997 – 2004 9005
1976 – 1977, 1981 – 1987 H4651
High Beam and Low Beam Headlight 1973 – 1975 H6024
1978 – 1980 H6054
Front Fog Light 1997 – 2004 893
1990 H3-55W
Back Up Light 1973 – 1987, 1997 – 2004 1156
1988 – 1990 890
Brake 1973 – 1982 1157
1983 – 1987 2057
1988 – 1989, 1997 – 2004 3057
1990 3157
Dome Light 1997 194
1977 211-2
1975 – 1976, 1978 – 1984, 1987 – 1989 561
1985 – 1986, 1990 562
1973 – 1974 578
1998 – 2004 912
Front Side Marker 1973 – 1979, 1982 – 1989, 1997 – 2004 194
1980 – 1981 194NA
1990 24NA
Front Turn Signal 1973 – 1982 1157
1983 – 1987 2057
1997 – 2004 4157
1988 – 1990 890
License Plate 1973 – 1990, 1997 – 2004 194
Parking Light 1973 – 1982 1157
1988 – 1989 194
1983 – 1987 2057NA
1990 3057
1997 – 2004 4157
Rear Side Marker 1979 168
1973 – 1978, 1980 – 1988, 1997 – 2004 194
1989 – 1990 24
Rear Turn Signal 1973 – 1982 1157
1983 – 1987 2057
1988, 1997 – 2004 3057
1990 3157
1989 890
Tail Light 1973 – 1982 1157
1990 194
1983 – 1987 2057
1988 – 1989 3057
Center High Mount Stop Light 1987, 1997 – 1999 1156
1988 – 1990 3155
1986 912
2000 – 2004 921
Courtesy 1976 – 1977 1004
1973 – 1974, 1978, 1980 1445
1983 – 1985, 1998 – 2004 168
1997 194
1979, 1990 561
1975, 1981 – 1982, 1986 – 1988 562
1989 73
Engine Compartment Light 1976 – 1980, 1982 1004
1988 – 1990, 1997 – 2004 561
1984 – 1987 89
Glove Box 1981 – 1982, 1985 – 1987 1891
1973 – 1977 1893
1978, 1980, 1983 – 1984 1895
1990 192
1988 – 1989, 1997 – 2004 194
Inner Tail Light 1997 – 2004 194
Map Light 1982 1004
2003 – 2004 12961
1997, 2000 – 2002 168
1987 211-2
1976 212-2
1990 24
1975 561
1986, 1988 562
1973 – 1974, 1977 – 1981 578
1998 – 1999 906
1984 – 1985 912
Outer Tail Light 1997 – 2004 3057
Radio Display 1973 – 1974 1816
1975 – 1982 1893
1983 – 1987 194
Trunk 1978, 1980 – 1987, 1989 – 1990 1003
1979 562
1973 – 1976 89
1988 912
1997 – 2004 920
Low Beam Headlight 2011 – 2013 H11
High Beam Headlight 2011 – 2013 H7
High Beam and Low Beam Headlight 2014 – 2017 9012
Front Fog Light 2011 – 2017 9145
Back Up Light 2011 – 2013 3157
2014 – 2017 921
Brake 2011 – 2013 3157
Daytime Running Light 2014 – 2017 7443
2011 – 2013 H11
Dome Light 2011 – 2017 194
Front Side Marker 2014 – 2017 194
2011 – 2013 194NA
Front Turn Signal 2011 – 2013 4157
2014 – 2017 7440NA
License Plate 2011 – 2013 12961
2014 – 2017 194
Parking Light 2011 – 2013 4157
2014 – 2017 7443
Rear Side Marker 2011 – 2013 3157
Rear Turn Signal 2011 – 2013 3157
2014 – 2017 7440
Tail Light 2011 – 2013 3157
Interior Door 2011 – 2017 578
Map Light 2011 – 2017 12961
High Beam and Low Beam Headlight 2011 – 2013 D1S
2014 – 2017 D3S
Front Fog Light 2011 – 2017 9145
Back Up Light 2011 – 2013 3157
2014 – 2017 921
Brake 2011 – 2013 3157
Dome Light 2012 – 2013 12961
2011, 2014 – 2017 194
Front Side Marker 2011 – 2017 194
Front Turn Signal 2012 – 2013 3457NA
2011 4157NA
2014 – 2017 PSY24NA
License Plate 2012 – 2013 12961
2011, 2014 – 2017 194
Parking Light 2012 – 2013 3357NA
2011 4157
Rear Side Marker 2011 – 2013 3157
Rear Turn Signal 2011 – 2013 3157
2014 – 2017 7440
Tail Light 2011 – 2013 3157
Interior Door 2011 – 2017 578
Map Light 2011 – 2017 12961
Low Beam Headlight 1991 – 1996 9006
High Beam Headlight 1991 – 1996 9005
Front Fog Light 1993 885
1991 – 1992, 1994 – 1995 H3-55W
Back Up Light 1993 – 1995 3057
1991 890
1996 921
Brake 1991 – 1996 3057
Dome Light 1993 – 1996 211-2
1991 – 1992 561
Front Side Marker 1991 – 1996 24
Front Turn Signal 1991 – 1992 3057NA
1993 – 1996 3157NA
License Plate 1991 – 1996 194
Parking Light 1991 – 1992 3057NA
1993 – 1996 3157
Rear Side Marker 1996 194
1991 – 1995 24
Rear Turn Signal 1991 – 1996 3057
Tail Light 1994 194
1991 – 1993, 1995 – 1996 3057
Center High Mount Stop Light 1991 – 1996 3155
Courtesy 1992 212-2
1991 24
1993 – 1996 562
Engine Compartment Light 1993 – 1996 561
1991 – 1992 89
Glove Box 1993 – 1996 1816
1991 192
1992 194
Map Light 1991 – 1994 212-2
Trunk 1991 – 1992 1003
1993 – 1996 920
Low Beam Headlight 1991 – 1996 9006
High Beam Headlight 1991 – 1996 9005
Front Fog Light 1993 885
1991 – 1992, 1994 – 1995 H3-55W
Back Up Light 1991 890
1996 921
Brake 1991 – 1996 3057
Dome Light 1993 – 1996 211-2
1991 – 1992 561
Front Side Marker 1991 – 1995 194NA
1996 24
Front Turn Signal 1996 3457NA
1991 – 1995 890
License Plate 1991 – 1996 194
Parking Light 1991 – 1992 3057
1996 3357NA
1993 – 1995 890
Rear Side Marker 1991 – 1996 24
Rear Turn Signal 1991 – 1996 3057
Tail Light 1994 194
1991 – 1993, 1995 – 1996 3057
Center High Mount Stop Light 1991 – 1996 3155
Courtesy 1992 212-2
1991 24
1993 – 1996 562
Engine Compartment Light 1993 – 1996 561
1991 – 1992 89
Glove Box 1993 – 1996 1816
1991 192
1992 194
Map Light 1991 – 1994 212-2
Trunk 1991 – 1992 1003
1993 – 1996 920
Low Beam Headlight 1985 H4656
High Beam Headlight 1985 H4651
Back Up Light 1985 1156
Brake 1985 2057
Dome Light 1985 561
Front Side Marker 1985 194
License Plate 1985 194
Parking Light 1985 2057NA
Rear Side Marker 1985 194
Rear Turn Signal 1985 2057
Tail Light 1985 2057
Front Inner Turn Signal 1985 2057NA
Front Outer Turn Signal 1985 194NA
Courtesy 1985 168
Engine Compartment Light 1985 89
Map Light 1985 912
Radio Display 1985 194
Trunk 1985 1003