Even if they're not illegal, they're still not considerate for oncoming drivers. A regular bulb type headlight housing is built so that all of the reflector surface, and the fresnel lens work together to aim the
very small source light the filament of an incandescent bulb out into a usable pattern, with minimal glare. Everything about the way a housing aims the light hinges around the size and location of the filament. HID bulbs are many times larger than the filament of a halogen bulb, and the whole thing glows just like a florescent bulb- there's no thin filament as the focal point of the housing, so the housing can't properly aim/distribute the light. This causes glare for oncoming traffic, and an unfocused light pattern for you to see with.
These are fine for a show car, but they definitly aren't an "upgrade" for a street car. If you have a two headlight system, you also lose the high/low beam function and end up with a beam pattern suited for neither driving in traffic (low beam/minimal glare), or back road/high speed driving where you need longer distance visibility.
I'm not knocking the vendor, just stating the facts about how these kits work. I've had friends with drop-in kits in their cars, and they've been pulled over for them. If you want a true upgrade that makes the light output use-able and responsible using HID's, you need to retrofit OEM HID projectors.
Halogen bulb on top (note the small filament) vs HID bulb on bottom. The whole HID bulb glows when lit- there's no way a halogen housing can aim the light coming from such a large light source.
If your light pattern isn't sharply cut off above eye-level, than you're causing unnecessary glare for oncoming drivers. Regular halogen bulbs/housings can get away with less of a sharp cut off since they're not as bright, but the intensity of HID's makes the cut off necessary to minimize glare to a reasonable level.
