HIDs have a ballast because they need very high voltage, but they draw very little current compared to a comparable conventional bulb in brightness.

 

what he said. ima just go with my silverstars for now.

 

The geometry of the reflector is based on the position of the light source (bulb) and it's characteristics. With the "plug and play" HID kits they rebase the bulbs to physically fit into our sockets however this completely throws off the placement and characteristics of the light source that our reflectors were designed for.

There are vehicles with OEM HID reflector setups (as opposed to projectors which are more commonly seen with HID) but the reflector design is optimized for that type of light, putting a halogen bulb in those housings would result in a crappy beam pattern just like you see when putting HIDs in a halogen housing. Incidentally using projectors designed for halogen with HIDs isn't much better.

The only way to get an optimal beam pattern with HID is to use a reflector or projector assembly designed for an HID source (what's commonly known as "retrofitting")

For those interested in more info here are some resources I dug up quickly (There are many more good resources out there, Google is your friend ):

http://www.supraforums.com/forum/sho...d.php?t=499137
http://www.intellexual.net/hid.html
http://www.hidretrofits.com/
http://www.hidplanet.com/forums/show...uths-and-Myths
http://www.hidplanet.com/forums/show...b-Crash-Course