A plug connector includes a mating tongue defining top and bottom surfaces thereon. Each surface is provided with a plurality of conductors in one row wherein the characters/categories of the conductors on the top surface are sequentially arranged to be same with those on the bottom surface with a pair of power conductors in two notches at two lateral side edges. The corresponding receptacle connector mounted upon a printed circuit board, defines a receiving cavity to receive the mating tongue therein. Opposite top and bottom rows of contacts are respectively located by upper and bottom sides of the receiving cavity and categorized essentially in a same sequence with the conductors of the plug connector for respectively connecting to the corresponding conductive pads, respectively. A pair of power contacts are located by two lateral sides of the receiving cavity to couple to the corresponding power conductor portions in the notches.