It is a valve adapter that is necessary when converting Benz AMG fog to HID. It is a necessary part when installing an external HID kit to a genuine halogen car (H7 equipped car). It can be installed not only on our HID kit, but also on other companies' products. * 1 set of this product will be 2 left and right (for 1 car). If you are unsure about compatibility, please contact us by phone at 03-6794-2003.