A connector includes an insulating housing, terminals assembled in the insulating housing, a first shell having a receiving space surrounded by a top plate, two lateral plates and a bottom plate for receiving the insulating housing therein, and a second shell having a base board electrically fixed on the top plate. Two sides of the top plate define two first openings spaced from each other and communicating with the receiving space. A rear side of each first opening extends forward to form an elastic arm with a free end arched downward into the receiving space. Two sides of the base board define two second openings corresponding to the first openings. A rear side of each second opening protrudes forward to form an extending arm resting against a top of the elastic arm for strengthening insertion and extraction strength of the elastic arms acting on a plug connector.