I put 15 watt LED's in place of the OEM halogens for the angel eye rings in my E53 and they certainly made a big difference. No more dull amber look, but a much brighter white light to the rings. They do stand out quite well in daylight and I now (as a matter of habit) simply turn the lights on to the first position (park lights) and use them as a daytime running light. I believe there are ways of wiring it up so they come on automatically or coding them as DRL's but for me, this is the simplest way...

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08/06 build 4.4i Stirling Grey over black