I figured I'd give these a try before putting them on our new Audi A6 4.2Q (mandatory Audi content) high beams. The bulbs DO have a bluish cast but do not have anywhere near the brightness of the Audi HID low beam system nor the light output of the previous 90/100W H4 halogen bulbs I was using on the Saab.

Furthermore, the PIAA bulbs quickly failed, in less than 4 months of everyday use, commuter, about 50 miles per day. One of the bulbs exploded and dusted/dirtied the inside of my Euro lamps which involve removing the lamp assembly and cleaning it out before a new bulb could be used.

Of course, being a glutton for punishment, I tried the bulbs on my 1990 740T volvo sedan. They were even worse than on the Saab. The best 9004's I've used have been bootleg Taiwan Phillips 90/100W capsules but the basic design of the Volvo USA headlight assembly is so bad that the PIAA bulbs compromised the nighttime drivability of the car to the point of being unsafe.

IMHO, the PIAA bulbs are overpriced, under-durabilitied (? word?), and underperformed. Don't waste your money.