Turns your rear signal lights into brake & running lights, so if you haven't done it already, you need to change the signal lights to red lenses or red bulbs. I also used the flash tab which flashes the brake lights 3 times before staying on. Hopefully, it'll wake up those cagers to the fact you're stopping. Of course, if they're texting............ Btw
, I had to use the equalizer that was included in the package to get my signals to flash properly even though I already had a no load flasher.