Quote Originally Posted by carl06GT View Post
but what does that do?
Re-read page 1. The 9007 bulb has two tungsten filaments in different positions so that the light reflects differently off the back of the housing.

HID bulbs only have one arc. To change the pattern of the light, you have to move the arc. The retracting motion works fine for H4 bulbs because the filaments are inline. The 9007 bulb filaments are next to each other.