What are HID's? Why install HID's? What is meant by Kelvin (K) color temperature? How do projectors work? What is the "cut off line", and how is it created? What are "Bi-xenon" projectors? What are Cold Cathode angel eyes? Why do some of the custom parts say "Not DOT" on your site?
What are HID's?
The best way to describe an HID or High Intensity Discharge headlight is to compare it to a more conventional halogen headlight. A halogen bulb consists of a wire filament surrounded by an inert gas. When electrical current is applied to the filament, it glows brightly to produce light. Contrast that with an HID bulb which has no filament, but instead consists of xenon gas, mercury, and metal halide salts. The xenon gas is ignited by an arc of high-voltage current and glows brightly. Also, the high voltage is supplied by a ballast, so in these respects it is like a fluorescent light. HID's are original equipment generally found on luxury and exotic cars but are progressively finding their way into the mainstream such as new BMW's, TSX's, and S2000's.
[- Back to top - ] Why install HID's?
The improved light output of HID's will give you a better field of vision and thus improved safety. They also look fantastic! HID's are 3 times brighter than your conventional 55w halogen bulbs, and illuminate everything in the cars path. When choosing an HID conversion kit, you will want to make sure you are receiving a warranty with them. Most HID conversion kits these days are not warranted and have a very high fail rate.
[- Back to top - ] What is meant by Kelvin (K) color temperature?
The Kelvin (K) is the unit of color temperature. 4300K is the brightest, most natural white light similar to that of daytime sunlight, and therefore the HID color temperature used most in the OEM automotive industry. When you look at the light coming directly out of an HID headlight, it possesses a bit of a blue or purple hue which most people recognize as the expensive, elegant look characteristic of HID's. For this reason, some HID kit manufacturers produce 5400K, 6500K, 8000K, etc. bulbs that give an even more distinct blue hue but at the expense of overall light output. For comparison, most halogen headlights have a color temperature around 3200K which gives them a "dingy" yellowish appearance compared to HID's.
Blue light is more fatiguing to the eyes, both to oncoming traffic and to the driver. Oncoming cars will see your lights for only a brief time, but as the driver, you must deal with it for the duration of your drive. The bluer the tint cast on the road and surrounding area, the more quickly your eyes become tired. It's a personal choice and I recognize and respect that some install HID's mostly for the look. However, very blue headlights might get you the wrong kind of attention from law enforcement. Personally, I'd like to benefit from my investment in the way of increased visibility and safety. Be aware that most of the 6500K and higher bulbs are produced by inferior manufacturers to capitalize on the marketability of "the bigger number must be better". Their 8000K bulbs may not measure 8000K. Don't be fooled.
[- Back to top - ] How do projectors work?
The reflector gathers as much light as possible so that it passes above the cutoff shield and gets evenly spread out by the curved lens:
A projector unit consists of:
a light source (bulb)
a reflector
a cutoff shield
curved lens
All components are designed to work together within small tolerances. Headlight manufacturers may use the same projector unit in headlights destined for different vehicles. This is cost saving. All a manufacturer has to do is have a nice looking round hole that the curved lens can peep out of.
Most projector units look roughly the same. They all have the same proportions-- long and skinny. The differences are diameter and depth, which is always proportional. The bigger the curved lens, the deeper the projector is.
[- Back to top - ] What is the "cut off line", and how is it created?
The cutoff line is the horizontal line where the beam turns from fully illuminated to almost darkness. If headlights are aimed correctly, the cutoff line should be within 50-100m in front of the car. The cutoff band is the area around the cutoff line that can contain various colors. These are the beautiful colors that you see when looking at projector lights from a distance.  The reflector shapes a rough cutoff above the shield. Then, the cutoff shield defines the final shape of a horizontal line on the wall separating darkness and light. Because a razor sharp beam cutoff is needed, the reflector beam is overlapping the cutoff shield edge, so that maximum intensity is kept close to cutoff line. The light that hits the gray cutoff shield will partially be converted to heat and partially deflected into stray light. 
[- Back to top - ] What are "Bi-xenon" projectors?
These projectors use solenoids to change the position of the metal shield that creates the cut off line, so that in one position "up" it acts as a cutoff to prevent light from blinding oncoming drivers, and in the other position "down" this restriction is removed for full brightness. The problem is that there are actually two solenoids in this package, one for pulling and one for holding, and consequently there is a 3-wire connector on the projector. For proper operation, the pull coil is supposed to be activated for about 1/10 - 1/5 of a second, and then turned off while the hold coil is still powered as long as high beams are desired. The hold coil alone is not strong enough to move the shield, only to hold it in the high- beam position. FX projectors on the other hand do not require a 3-wire set up, but rather just two wires that allow a much easier set up as well as install. Below are a couple of videos of a dual FX35 bi-xenon projector set up for an '07 Jeep Grand Cherokee:
[- Back to top - ] What are Cold Cathode angel eyes?
Cold Cathode Fluorescent Lighting (CCFL) is in essence a variation of the technology used in fluorescent light bulbs. These angel eye rings produce the absolute brightest, most consistent light output and provide the most aesthetically appealing appearance as well.
[- Back to top - ] Why do some of the custom parts say "Not DOT" on your site?
In the USA, headlights are only legal for use on public roads if they are DOT approved. (Similar laws apply in all other "developed" countries and many other countries.) This requires that samples of the headlights be sent to the proper testing laboratory and certification must be obtained that the design is approved. Approval is only with specific bulbs tested in the lab in the samples and DOT approval is invalid if a different bulb is used.
It is illegal to use on public roads home brew headlights or headlights using a bulb other than what they were DOT-approved to use. For example, a headlight that is DOT approved and normally uses a 9005 halogen bulb is almost certainly not DOT approved for anything else - especially not a D2S for example.
Many HID conversion kits come with disclaimers to the effect of "off road use only". Such disclaimers may appear in the kit seller's ads, web site, or on the kit packaging. Less honest retrofit outfits may merely fail to let you know that such a retrofit is not road-legal. More dishonest retrofitting outfits may even falsely claim that their headlights or ones modified with their product/service are road legal.
DOT requirements have lower and/or upper limits (sometimes both) on candela ("beam candlepower") into many different directions, as in various angles above, below, and to each side of straight ahead. In the unlikely event your headlight meets all of these and other technical requirements, it is still illegal unless it is submitted for testing and certification.
As for what can happen if you use illegal headlights?
1. Often enough, nothing. This depends on location. In some USA cities, law enforcement of traffic regulations in general is lax. Police are generally not equipped to do headlight photometry anyway.
2. Some unlawful HID retrofit headlights are obvious to a few cops. It is more obvious if you have the really bluish or aqua-ish or obviously fake HID bluish headlights that are known to some cops to be a safe bet to not meet the complex photometric and colorimetric standards.
If the cop believes you have unlawful headlights, you can be stopped and ticketed. Depending on your state, the violation may be having an invalid inspection sticker or whatever violation of headlight law. Depending on your state and the mood of the cop, you may in extreme cases be barred from driving the car at night (or at all) until it has legal headlights and it has passed inspection again with the legal headlights.
3. Excessive light in some directions can dazzle other drivers. It is possible for you to be legally liable if this causes or contributes to an accident. Modified headlights might have insufficient light in some directions, and you could be held legally liable if that causes or contributes to an accident.
4. You may have trouble with your insurance company if you have an accident while driving a car that cannot legally pass inspection or has fraudulently passed inspection, even if the inability to legally pass inspection did not contribute to the accident. You might also have trouble with your insurance company if you are cited for driving without valid current inspection stickers or are cited for having fraudulently passed inspection.
Note that at least in some states, "off road" lights must be inoperative when driving on a public road. This may mean having opaque covers on the lights and/or having wiring to the lights disconnected.
With all of this said, it is safe for Izn Trbl Inc. to state "All custom made headlight and tail light parts are not DOT, and should be used for shows or off road only", even though all of our lights have better output and function better than stock lights, and use DOT OEM parts from other vehicles.
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