It is a valve adapter that is necessary when converting a Honda H1 car to HID. When installing an external HID kit to a genuine halogen car (H1 equipped car), it is a necessary part depending on the car model. 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.