The D1 HID bulb is OEM light with the igniter in its base. They are similar to D3 bulbs, though these lights are not interchangeable. D1 bulbs operate on higher voltage. They are used for the low beam (2004-2009 Cadillac XLR) or perform for both high and low beams (2010-2014 Volkswagen GTI with HIDs).
You can find two options: D1S and R sizes. The first is used for the projectors which have shield creating the cut off line to prevent the blinding. The D1R bulbs have a painted section and can be installed to the reflector housing preventing the excessive glare. You will be pleasantly surprised with available color options. Kensun D1 bulbs can be used as a direct replacement of OEM bulbs and used with the factory ballasts.
Those who are tired of Xenon lights can choose Kensun offers D1 LED bulbs. LEDs have chips which are durable and have a long lifespan. These bulbs come with color filters so you can choose the most comfortable color for driving (blue, yellow or white). LED bulbs do not require the ballasts that is why they should be removed. Professional installation may be needed.