PIAA Anti-Vibration Ultra White Bulb. After getting tired of the wimpy low beam on my Ducatis, I decided to upgrade to the PIAA Extreme White H4 bulb. The H4 replaces the stock bulb on the following models:
Other model fitments unknown
Simple plug in design that is identical to the stock plug and shape. The light color is 3800K, or white in the range from blue to Yellow. The stock bulb puts out a light that is 3200K in color, so the PIAA is much whiter. This light will be brighter for daytime visibility/safety, and will be plenty bright enough for all of your nighttime riding. Because the low beam puts out the light equivalent of a standard high-beam, you should set up the angle of your headlight so as to not offend oncoming traffic.