When doing replacement or upgrading on 2006 – 2018 Volkswagen GTI with capsule halogen headlamps HID LED Lights Tail without, the bulb size guide is necessary for you to take the reference.
Jump to corresponding car model with the catalog bellow.

Low Beam Headlight 2006 – 2018 H7
High Beam Headlight 2010 – 2017 H15
2006 – 2009 H7
2018 H9
Front Fog Light 2007 – 2009 9006
2006 H3-55W
2010 – 2014 H8
Back Up Light 2006 – 2009 1156
2014 – 2018 921
Brake 2006 – 2009 1156
2015 – 2018 7440
Daytime Running Light 2010 – 2018 H15
Dome Light 2006 – 2009 578
2010 – 2014 DE3423
Front Side Marker 2010 – 2014 12256
2006 – 2009, 2015 – 2018 12961
Front Turn Signal 2007 – 2009 1156
2006 3457
2010 – 2014 PSY24WSV
2015 – 2018 PWY24WNAHTR
License Plate 2006 – 2009 12844
2010 – 2013, 2015 – 2018 12961
Parking Light 2010 – 2014 12961
2007 – 2009, 2015 – 2018 194
2006 3457
Rear Side Marker 2006 12814
2007 – 2009 12961
Rear Turn Signal 2006, 2009 1156
2015 – 2018 7440
2010 – 2014 7440NA
2007 – 2008 P21W
Tail Light 2007 – 2009 1156
2006 12814
2015 – 2018 7440
Luggage Compartment 2006 12961
2010 – 2014 578
2007 – 2009, 2015 – 2018 6411
Door Mirror Illumination Light 2007 – 2014 194
Glove Box 2007 – 2018 12256
2006 12961
Interior Door 2006 194
Map Light 2006 – 2018 12961
Rear Reading Light 2018 12961
Stepwell 2007 – 2014 12256
Low Beam Headlight 2006 – 2009 D2S
High Beam Headlight 2006 – 2009 H7
High Beam and Low Beam Headlight 2010 – 2014 D1S
2015 – 2018 D3S
Front Fog Light 2006 – 2009 9006
2010 – 2014 H8
Back Up Light 2006 – 2009 1156
2014 – 2018 921
Brake 2006 – 2009 1156
2015 – 2018 7440
Dome Light 2006 – 2009 6411
2010 – 2014 DE3423
Front Side Marker 2010 – 2014 12256
2006 – 2009 12961
Front Turn Signal 2006 – 2009, 2015 – 2018 H21W
2010 – 2014 PSY24WSV
License Plate 2006 – 2009 12844
2010 – 2013, 2015 – 2018 194
Parking Light 2006 – 2014 194
Rear Side Marker 2006 12814
2007 – 2009 12961
Rear Turn Signal 2006 – 2009 1156
2015 – 2018 7440
2010 – 2014 7440NA
Tail Light 2007 – 2009 1156
2006 12814
2015 – 2018 7440
Luggage Compartment 2006 12961
2010 – 2014 578
2007 – 2009, 2015 – 2018 6411
Door Mirror Illumination Light 2007 – 2014 194
Glove Box 2007 – 2018 12256
2006 12961
Interior Door 2006 194
Map Light 2006 – 2018 12961
Rear Reading Light 2018 12961
Stepwell 2007 – 2014 12256
Front Fog Light 2010 – 2013 H8
Back Up Light 2010 – 2013 921
Dome Light 2010 – 2013 DE3423
Front Side Marker 2010 – 2013 12256
Front Turn Signal 2010 – 2013 PSY24WSV
License Plate 2010 – 2013 194
Rear Turn Signal 2010 – 2013 7440NA
Luggage Compartment 2010 – 2013 578
Door Mirror Illumination Light 2010 – 2013 194
Glove Box 2010 – 2013 12256
Map Light 2010 – 2013 12961
Stepwell 2010 – 2013 12256
Front Fog Light 2010 – 2013 H8
Back Up Light 2010 – 2013 7440
Brake 2010 – 2013 921
Dome Light 2010 – 2013 DE3423
Front Side Marker 2010 – 2013 12256
Front Turn Signal 2010 – 2013 PSY24WSV
License Plate 2010 – 2013 194
Rear Turn Signal 2010 – 2013 7440NA
Tail Light 2010 – 2013 921
Luggage Compartment 2010 – 2013 578
Door Mirror Illumination Light 2010 – 2013 194
Glove Box 2010 – 2013 12256
Map Light 2010 – 2013 12961
Stepwell 2010 – 2013 12256