When doing replacement or upgrading on 2017 – 2018 Hyundai Ioniq 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 Headlight2017 – 2018 H7
High Beam Headlight2017 – 2018 9005
Back Up Light2017 – 2018 921
Brake2017 – 2018 1157
Dome Light2017 – 2018 DE3175
Front Side Marker2017 – 2018 168
Front Turn Signal2017 – 2018 2357NA
License Plate2017 – 2018 168
Parking Light2017 – 2018 168
Rear Side Marker2017 – 2018 168
Rear Turn Signal2017 – 2018 1156
Tail Light2017 – 2018 1157
Trunk2017 – 2018 DE3423
High Beam and Low Beam Headlight2017 – 2018 D3S
Back Up Light2017 – 2018 921
Dome Light2017 – 2018 DE3175
Front Side Marker2017 – 2018 194
Front Turn Signal2017 – 2018 2357NA
License Plate2017 – 2018 168
Trunk2017 – 2018 12844