These adaptors will enable you to install an HID Kit using your stock headlights. Some vehicles have an adaptor that locks / secures the factory halogen bulb into place. These pre modified adaptors will take the place of the stock adaptor as they have been designed to both accommodate an HID bulb and lock it into your vehicle's stock headlight housing. You have to use these adaptors or modify your stock ones if your vehicle uses an adaptor to secure the stock bulb. You cannot simply install the HID bulb without the adaptor, as you will not be able to secure the bulb.