I get the feeling that im going to be repeating myself till im blue in the face here about HID retrofit kits so i've just copied and pasted a post i made a few months ago;
Whilst i hate the people that do it, i think the retailers are equally to blame. They dont inform you that they are illigal for road use and will fail an MOT unless you go digging through their FAQ. This is an example i found a while ago and used a lot since;
The left light is an HID in a projector housing (what HID's are designed to be fitted in) and left is an HID in a reflector housing, designed to focus a halogen bulb, which emits light in totally different way to an HID.
I think the worst is people that say they just aim them down and they are fine, because they are admitting that they are aware they're causing a problem and being a danger to other road users, yet have absolutely no idea what they are talking about and dont bother doing the research into why they are so blinding.
Ignoring all of the legality issues and trying to get around them, fitting an HID kit into anything other than a projector headlight assembly will blind oncoming traffic. This will get you points, a fine, and a lot of ****** off other motorists, not to mention the guilt you will have to live with if you cause an accident. The light pattern emitted by either an HID or and LED retrofit bulb is completely different to the light output of a Halogen bulb, hence the reason projector assemblies were invented. Below is a photo showing the difference in beam pattern between an HID conversion kit fitted into a reflector housing and a proper projector retrofit unit;
So here is a retrofit kit in a reflector housing;
And here is what it should look like in a projector assembly;
There are a lot of selfish motorists out there that know all of this and still choose to ignore it, and its one of my biggest hates on the road. Luckily police certainly up here are really starting to crack down on it, i imagine everywhere is now the same or at least not far behind.
Rich