An electrical connector includes a housing and a pair of contact wafers. Each contact wafer includes an insulative plate and a plurality of contacts. The contacts include a plurality of grounding contacts and plural differential-pair contacts. Each contact includes a contacting section extending beyond a front edge of the plate, a tail section exposed outside of a bottom edge of the plate and a connecting section linked between the contacting section and the tail section. The plate includes a plurality of first through holes formed along the connecting section of each grounding contact, and a plurality of second through holes formed along the connecting sections of each pair of the differential-pair contacts. The first through holes and the second through hole are essentially offset from each other in both the first direction and the second direction which are perpendicular to each other.