An electrical connector includes a housing and a plurality of ground wafers and signal wafers. A front side is configured to mate with a mating connector. The ground wafers and signal wafers are stacked next to one another along a stack axis. The ground wafers are interleaved between adjacent pairs of the signal wafers. Each signal wafer includes at least one signal conductor held by a signal holder that is composed of a first material. Each ground wafer includes at least one ground conductor held by a ground holder that is composed of second material. The second material is a lossy material and the first material is a low loss dielectric material that has a loss tangent that is lower than a loss tangent of the lossy material. The signal conductors and the ground conductors are configured to engage and electrically connect to the mating connector.