When doing replacement or upgrading on 2004 – 2011 Mazda RX-8 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 Headlight2004 – 2011 H7
High Beam Headlight2004 – 2011 H9
Front Fog Light2009 – 2011 9006
2004 – 2008 H8/H11/H16
Back Up Light2004 – 2008 7440
2009 – 2011 921
Brake2004 – 2008 7443
Dome Light2004 – 2011 DE3175
Front Side Marker2009 – 2011 1157NA
2004 – 2008 194
Front Turn Signal2009 – 2011 1157
2004 – 2008 7440NA
License Plate2004 – 2011 12961
Parking Light2009 – 2011 1157
2004 – 2008 12961
Rear Side Marker2009 – 2011 12961
Rear Turn Signal2004 – 2011 7440NA
Tail Light2004 – 2008 7443
Center High Mount Stop Light2004 – 2011 7440
Courtesy2004 – 2011 12961
Map Light2004 – 2011 12961
Trunk2004 – 2011 194
Low Beam Headlight2004 – 2011 D2S
High Beam Headlight2004 – 2011 H9
Front Fog Light2009 – 2011 9006
2004 – 2008 H8/H11/H16
Back Up Light2004 – 2008 7440
2009 – 2011 921
Brake2004 – 2008 7443
Dome Light2004 – 2011 DE3175
Front Side Marker2009 – 2011 1157NA
2004 – 2008 194
Front Turn Signal2009 – 2011 1157
2004 – 2008 7440NA
License Plate2004 – 2011 12961
Parking Light2009 – 2011 1157
2004 – 2008 12961
Rear Side Marker2009 – 2011 12961
Rear Turn Signal2004 – 2011 7440NA
Tail Light2004 – 2008 7443
Center High Mount Stop Light2004 – 2011 7440
Courtesy2004 – 2011 12961
Map Light2004 – 2011 12961
Trunk2004 – 2011 194