HL68137 Projector Headlamp, 90mm Low Beam Module, each. DOT Halogen H9
This high performance headlamp is designed specifically for custom applications. It is a weatherproof, and easily mounted to any vertical surface.
Includes:
Lamp,
H9 Halogen bulb
Adjuster Screw Kit.
$59.75

So you've read about HID headlamps and have it in mind to convert your car. A few mouse clicks on the web, and you've found a couple of outfits offering to sell you a "conversion" that will fit any car with a given type of halogen bulb. STOP! Put away that credit card.

An HID kit consists of HID ballasts and bulbs for "retrofitting" into a halogen headlamp. Often, these products are advertised using the name of a reputable lighting company ("Real Philips kit! Real Osram kit! Real Hella kit!") to try to give the potential buyer the illusion of legitimacy. Fact: While some of the components in these kits are sometimes manufactured by the companies mentioned, the components aren't being put to their designed or intended use. Reputable companies like Philips, Osram, Hella, etc. never endorse this kind of "retrofit" usage of their products.

Halogen headlamps and HID headlamps require very different optics to produce a safe and effective—not to mention legal—beam pattern. How come? Because of the very different characteristics of the two kinds of light source.

A halogen bulb has a cylindrical light source: the glowing filament. The space immediately surrounding the cylinder of light is completely dark, and so the sharpest contrast between bright and dark is along the edges of the cylinder of light. The ends of the filament cylinder fade from bright to dark. An HID bulb, on the other hand, has a crescent-shaped light source -- the arc. It's crescent-shaped because as it passes through the space between the two electrodes, its heat causes it to try to rise. The space immediately surrounding the crescent of light glows in layers...the closer to the crescent of light, the brighter the glow. The ends of the arc crescent are the brightest points, and immediately beyond these points is completely dark, so the sharpest contrast between bright and dark is at the ends of the crescent of light.

This diagram shows the very different characteristics of the filament vs. the arc:


When designing the optics (lens and/or reflector) for a lamp, the characteristics of the light source are the driving factor around which everything else must be engineered. If you go and change the light source, you've done the equivalent of putting on somebody else's eyeglasses: You can probably make them fit on your face OK, but you won't see properly.

Illegal Xenon retrofitting is dangerous and illegal
Vehicle certification loses validity, insurance protection is restricted - up to 100 times higher glare values
Article of 10.10.2002
Lippstadt, October 2002. People who just buy a xenon headlamp set including cables, xenon light source and ballast, remove the halogen bulb from the headlamp, saw a hole in the cover cap, insert the xenon ulb in the reflector and connect the electronic ballast with the on-board power supply are endangering other road users through extreme glare and are acting against the law: the vehicle certification loses its validity and insurance protection is restricted. Only complete, type-approved xenon headlamp sets including an automatic headlamp levelling and lens cleaning system are legal.

This is why it is illegal to make a halogen headlamp into a xenon headlamp:

In Europe only complete xenon headlamp systems may be retrofitted. They comprise a set of type-approved headlamps (with the E1 mark on the outer lens, for example), an automatic headlamp levelling device and lens cleaning equipment (compulsory according to ECE regulation R48 and § 50 STVO, section 10(Germany only)).

Every headlamp is given its type approval together with the light source (halogen or xenon) it is operated with. If the light source is replaced by one which is neither type-approved nor designed for the type approval of the headlamp, this type approval becomes invalid, as, consequently, does the vehicle's certification (§19 STVZO, section 2, sentence 2, no. 1(Germany only). Driving without vehicle certification leads to restrictions of insurance protection (§ 5, section 1, no. 3 KfzPflVV(Germany only)). People who sell such non-type-approved lighting equipment must expect claims for damage from buyers. Because in passing on these parts, the seller not only takes over the guarantee that they may only be used for the designed purpose but also, under some circumstances, damage risks to an unlimited amount. High glare values: From measurements made under laboratory conditions Hella specialists have found that the active beam pattern of a headlamp developed for halogen bulbs, but operated illegally with a xenon light source, no longer corresponds to the originally calculated values. In the case of reflection systems, glare values have been measured which exceed the permissible limiting values 100 times over. The headlamps of these vehicles no longer have a cut-off line and cannot be adjusted either. The glare values correspond to the those of driving lamps. This puts other road users in great danger.