Halogen bulbs may have their own unique way of being secured inside a headlight. Some LED conversion kits (ex. H7 bulbs) generally cannot be installed in a headlight without the use of an adapter. An adapter is a physical product which secures an LED bulb in a headlight. Always examine your vehicle's headlights first before purchasing an LED conversion kit so you can determine how the bulb is secured in place, and whether or not you will need an adapter. For example, H7 bulbs are notorious for having a variety of different ways of being secured in a headlight, as are H15, 9004 and 9007 bulbs. So for those, you will need an adapter. Others such as 9005, 9005, H11, H13 are straight forward and do not require bulb adapters.