A plug connector mateable with the receptacle connector, includes an insulative housing enclosed in a metallic shell, defining a receiving cavity to receive the mating tongue, and equipped with a plurality of contacts on opposite sides in the vertical direction. A latch forms a pair of locking heads extending into two opposite lateral sides of the receiving cavity to lock with a shielding plate embedded within a mating tongue of the complementary receptacle connector during mating. The plug connector is equipped with a pair of locking screws symmetrically located by two sides of the metallic shell and aligned with the pair of locking heads in the transverse direction, and the receptacle connector is equipped with a pair of screw holes to receive the pair of locking screws in a locked manner.