a first mating interface comprising a first receiving space with a first tongue received therein, and a plurality of first contacts retained therein, the first contacts comprising a plurality of first elastic contacts and a plurality of first flat contact, each first elastic contact having a securing portion fixed in the first mating interface, an elastic contact portion extending to the first tongue and a soldering portion, each first flat contact having a retention portion retained in the first mating interface, a flat contact portion extending to the first tongue and a tail portion, the first tongue having a pair of opposite upper face and lower face; and

a second mating interface stacked with the first mating interface along a thickness direction of the first tongue, a plurality of second contacts retained in the second mating interface;

wherein the flat contact portions and the elastic contact portions are located at a same side of the upper face, and are arranged in two rows along a length direction of the first tongue, wherein a geometric profile of the first tongue is substantially same as what of a standard USB 2.0 A type receptacle, wherein the first elastic contacts are adapted for USB protocol and an arrangement of the first elastic contacts is compatible to a standard USB plug, wherein the first tongue defines a plurality of first passageways depressed from the upper face and a plurality of second passageways depressed from the lower face and communicating with the first passageways, the retention portions are received in the first passageways, and the fiat contact portions are received in the second passageways, wherein the first tongue defines a plurality of third passageways depressed from a lower face thereof, and the elastic contact portions are assembled in the third passageways and extend out of the lower face, the second passageways and the third passageways are arranged in two rows along the length direction and discontinuous with each other, wherein the first fiat contacts comprise two pairs of differential signal contacts and a grounding contact located therebetween, and the fiat contact portions of the signal and grounding contacts are juxtaposed with respect to each other in a width direction of the first tongue, wherein the second mating interface is different from the first mating interface.