For use when hyper flashing or fast flashing occurs. This will typically happen when converting to ALL LED in your auto and using bimetallic flashers. The smaller current flow of the LED, 300ma LED vs 2-3 amps filament bulb, does not sufficiently heat up the bi metallic strip in the flasher, thus causing a fast flash.

These are power resistors packaged with quick connects and are connected from the flashing connection of the LED to ground.