BMW E39 owners who are considering upgrading their original halogen bulbs to HIDs will find that the HID bulb isn't a straightforward replacement due to the design of the housing clip. To simplify this process, these specialized adapters have been introduced. Before making a purchase, owners should inspect their headlights for a specific plastic socket behind the bulb to determine if these adapters are required. All E39 housings are designed to accommodate H7 bulbs, with the original part designed to extend the +/- connector to the electrical socket. These adapters have been meticulously designed with a slotted structure that allows the bulb's wiring to enter from the side. Once inserted, the bulb is securely held in place by the original clip assembly, ensuring it remains as firm as the stock setup.