The “R” HID bulbs have a black stripe on the glass capsule to defuse the light and reflect glare. They are used in applications without a projection headlamp. “S” HID bulbs are used in headlamps with a projector system.
The D1 and D2 bulbs contain mercury and are used in older applications. The newer and improved versions of Xenon bulbs are the D3 and D4 bulbs. These do not contain mercury and are used in the majority of newer cars.
The D1 and D3 bulbs have an electronic high-voltage starter integrated into the base.
The operating voltage of D1-D2 bulbs is 85 volts, while D3-D4 operate on 42 volts.
