Single beam HID kits (H1, H3, H7 etc.) do not require a relay. Single beam bulbs are where the light is only used as a dip beam (regular driving light).
Dual beam / Bi-Xenon HID kits.
This type of the kit requires a relay so that the solenoid within the bulb, typically (H4) which then pitches the bulb upwards allowing for the “high” beam or “flash” function.
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