Single beam HID H7 bulbs are extremely bright. They throw the light 3 times further than the halogen bulbs do. These lights can be used either for the high or low beams of the headlight, in this case, 2 kits are needed to convert both beams, like for 2003-2009 Volkswagen Golf and 2008-2013 Mercedes C Class with composite housing. An HID system consumes much less power and as a result, it is more efficient and provides the longer lifespan.
Usually, the H7 bulbs are of spring clip type. That is why in specific cases they may require the installation of spacers/holders to make the bulb fit the headlight housing properly. Some OEM spacers can be used with the aftermarket set.
There are cases when the H7 HID bulb power wire cannot be connected to the vehicle stock harness socket, the slight modification may be required. The leads should be removed from the HID factory connector.
LED lights are 90% more efficient than incandescent bulbs. All LEDs have a fan which is around 3 cm that is why there should be enough space behind the headlight housing. H7 LEDs with Cree Chips come with the removable locking ring. This locking ring can be installed to the housing at first and then the bulb can be locked in its place.