Real Quick Question.

[Alan]

My buddy has a B6 A4, and is looking to put HID's in. I wasn't sure, as I have a B5, if HID's could be fitted directly into his current housings, or if he needs different housings.

[scorneil]

You can put HID's into halogen housings. Kit here:
http://www.hidconcepts.com/Kits-valeo-d2s.html

the better solution is to get the Xenon housings.

Watch the classifieds, there are always housing in there.