Many headlights have a little bulb located in, or near the high beam reflector, which lights up anytime the parking lights are activated (generally at night when the low beams come on). A typical city light is just a clear bulb that lights up dingy yellowish color. Swap that little sucker out with a high power LED bulb, and it's entire section of the headlight is going to light up with crisp, clean, white LED light, giving an entirely new look to the car.
