This part actively regulates the cooling function of the radiator grille using an electronically controlled flap (cover). The lid is closed to reduce unnecessary air inflow and improve aerodynamic performance and fuel economy depending on the situation. Of course, when cooling is required, the lid is opened to let outside air into the radiator. It began to be housed in cars as the accuracy of engine cooling control improved. Some models accommodate active air flaps that control left and right respectively to increase stability in corner driving.