So one of the bulbs is failing the light is pink in colour (swapped bulbs around and the fault follows the bulb), so looking at replacement. The ones that are current fitted are Osram D2S 35W 66040. These bulbs look to have been revised to 66240. I've checked Audi's prices and they are around £120 per bulb which is a total rip off, seeing as you can get Osram bulbs for around £30 each. So one of the options is nightbreaker range OSRAM D2S 66240XNB 66240XNB NIGHTBREAKER UNLIMITED NBU 35W XENON HID BULBS | eBay the question is are the nightbreaker bulbs any better are they worth the extra £50 for a pair. I'm also going to replace both bulbs as they are the same age.