A first connector includes a first insulative housing defining opposite first and second mating faces, a set of first upper contacts arranged upon the first mating face, a set of first lower contacts including a first lower differential pairs, a second lower differential pairs and a lower grounding contact, and a first grounding plate. The contacting sections and the first grounding arm are arranged upon the second mating face, and the first terminal portions of the first lower differential pairs are arranged in a first row, and the second terminal portions of the second lower differential pairs and the tail section of the lower grounding contact are arranged in a second row for excellent high-frequency characteristics.