An apparatus, system and method for facilitating the calibration and measurement of differential devices by a variety of laboratory fixtures. An adapter is used to transition the connection of standard coaxial interfaces to a hermaphroditic differential interface while compensating for discontinuities on impedance at the connection. The adapter includes a transition region with conductors and shield dimensions that compensate for the discontinuity in impedance. The adapter has pin and socket inputs so that a mated pair of the adapters provides an insertable device for test and measurement on a four port vector network analyzer.