I've tried the regular Silver Stars and the Ultras... and like HIR's the best. The SS's definitely have a nice white light but I found when driving in rainy conditions they tend to lack a bit. The HIR's are actually much brighter and can be modified to fit in 9005 and 9006 housings. They are expensive though and aren't quite as white as the SS's but are much better in the rain and the dry. The only thing I'm unsure of so far is longevity since the filament burns a little hotter (they burn hotter due to the infrared reflective coating, which reflects heat back to the filament to burn hotter and thus brighter. The coating is not put on the top of the bulb so the light will go through unobstructed. The bulbs have the standard 55/65 watt rating of the 9006/9005 bulbs respectively).
Brightness wise... the low beams have a higher lumen rating than the Silver Star high beams and so far in my Z and M30 have not caused any additional glare.
It is technically an "off-road" modification as you aren't supposed to put a bulb in brighter than what the housing was designed for or something along those lines... but, unlike those hid "kits" floating around everywhere, you aren't likely to have any trouble from the police, especially not having an extreme white/blue look to it.
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