Socket connector assembly and plug connector

A socket connector assembly comprising a receptacle connector, said receptacle connector forwardly defines a first slot and a second slot, the second slot opposite the first slot disposed rearwardly displaced a distance , corresponding to the contacts in order to avoid interference position of the two slots. Corresponding mating plug connector comprises two horizontal circuit board mating distal arranged offset in the longitudinal direction. The receptacle connector of the present invention is smaller height conditions for the realization of doubling transmission speed, and may be compatible with an existing plug connector.