Universal 50W AMP Ultra Slim Ballast (GTR.BL031)Description This is the 5th Generation HID ballast: designed specifically to integrate with the complex computer systems found in modern vehicles. PWM Integration: PWM stands for Pulse Width Modulation, it's when the vehicle flashes the input voltage to your bulbs so fast that you can't see the difference, but it modulates the activity of the halogen bulb. That's fine on an old style halogen incandescent, but on HID systems it might make a flashing or