A receptacle connector includes an insulative housing defining a base and a mating tongue extending from the base with a widen and thicken step structure formed around a root of the mating tongue near to the base, two rows of plate contacts disposed in the insulative housing with contacting sections exposed upon the mating tongue and in front of the step structure and categorized with signal contacts, power contacts and grounding contacts, and a metallic shielding plate disposed within a middle level of the mating tongue and occupying most portions of said mating tongue. The shielding plate defines a pair of immoveable and un-deflectable lateral edge sections in front of the step structure, each lateral edge section is configured to be adapted to be locked with a latch of a plug connector in a transverse direction.