Each headlight unit consist of a ballast unit to drive the necessary power for the headlight. All low beam kits also have a voltage regulator unit to compensate for DRL systems, extended periods of use, ECU voltage checks etc. They also aid in preventing flickering. High beam units do not need the additional voltage regulator units.
The custom F150LEDs.coms voltage control unit look like this;
Please see the image below for the ordering of the units.
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