currently installing relays for headlamp upgrade, doing this on both bricks as a winter project.
found the website attached while surfing "inter-web" for H4 bulb information.
pretty informative and discounts a lot of the hype surrounding improved and overpriced bulbs.
as with most things you'll choose what you like, can afford and think works well but it's always good to be armed with a little knowledge before purchasing something that doesn't perform as expected or advertised.
http://www.danielsternlighting.com/tech/tech.html
