Alright, as an attempt to stop the repeat H.I.D. posts, here is the answer to almost every H.I.D. question you can come up with. If any thread is posted in this section where the answer can be found here, it will be locked.
"Can I put a H.I.D. kit in my factory headlight housings?"
Yes and no. They will "work" and will fit if there is a kit made in your size (refer to Everything Bulbs to find out what size you'd need)
The downside is that the headlight housing provided by the factory reflector halogen setup (this includes both pre and post 2005 headlights, and ST170s and their equivelants) is not set up for the amount of light, or lumens put out by the HID bulb. Also, the bulb is shaped differently, so not only is MORE light being put out, but its being reflected differently by the headlight housing becuase the bulb location is altered. This makes for a dangerous amount of glare for oncoming traffic relative to that of your high beams being on all the time. I'm not going to post pictures of glare because camera's are usually inaccurate ways of capturing exactly what it looks like, but I think its pretty self explanitory.
Another thing is that people think any aftermarket projector can handle the output of a H.I.D. setup. This is not true. Not only with the light pattern be awefull with ANY of the cheap ebay kits you can buy, but the projector is not built with the intent of harnessing the light output of a H.I.D. setup. Glare will be almost if not as bad as that of a stock reflector housing. If you are going to put a H.I.D. kit in any aftermarket projector headlight housing, either buy Hella's or retrofit a H.I.D. safe projector into the housings you currently have. It is no better than having a stock headlight if you just slap a kit in the low grade projectors that are currently in the cheap projector housings.
Also, you may think "Well the cutoff is still good on my stock headlights even with my H.I.D. kit". The cutoff is not what causes this glare. The cuttoff can be as sharp as can be, its the scattered amount of light above the cutoff that forms the glare. It doesnt have to be bright light to cause glare. Not only is it irresponsible, but its illegal.
Now another common topic is retrofitting. Retroffiting is utilizing the housing you have and adapting it to accomidate for a legal and safe setup. A great resource I use myself in researching retrofitting techniques and other H.I.D. information is the HIDPLANET.COM forums. The people on this site know exactly what it takes to get the ideal setup, and will help you out more than I can on this subject.
Now for the Kelvin rating (ex. 5000k). Most factory setups use a 4300k rated bulb, which is very close to the color of the sun's light which in turn emits the most usable light. A common misconception is that the higher the K rating, the brighter the light. That's incorrect. The higher the K rating simply means that the bulb color is getting further from that of natural sunlight and further toward that of ultraviolet, which is completely useless light to the human eye (black light).
Here is an idea of what each K rated bulb will emit for light:
This Kelvin rating will put out a light similar to that of the early morning or just before sunset. A very yellow light.
This is equal to that of the afternoon sun. Clean white light, very little yellow.
This is the color rating of an electronic photo flash. Pure white light.
This is where the light starts getting blue. You'll notice it to to be about the color of light put out by a clear sky, white with a blue tint.
This is completely blue. Usable light is almost non existant. At this point your headlights are about as usable as the average blue coated "HID Look" halogen.
These are pretty much useless for a street setup. You're light is very purple, which makes for a hard time seeing dry pavement, and wet pavement becomes almost invisible...A show only setup.
I'll be adding more as I think of things, but this should help out anyone looking for information regarding adding HID's to their car. Please just be responsible and consider other's when upgrading your cars lighting setup. Last thing you need is someone going off the road and blaming your illegal headlight setup for blinding them...Insurance companies don't like to hear this, and you'll probably get a hefty fine from your local police department.
Resources For More H.I.D. Information
If anything you wanted to know has still not been answered. Please use the Search Feature and try to find what you're looking for before starting a new thread. Thanks.