A connector insert arrangement (40a, 40b, 40', 40'', 40"') receivable in a connector housing (20, 30) of a connector for removable engagement with a complementary connector, said connector insert arrangement (40a, 40b, 40 ', 40'', 40''') comprising: a plurality of dielectric inserts (94, 94' 100) each of which supports one or more electrical contacts (110, 114) for access by the complementary connector at a first insert surface of each dielectric insert (94, 94' 100) and each of the dielectric inserts (94, 94' 100) defines an opposing, second insert surface and each electrical contact (110, 114) is selected as one of a contact pad and a spring probe pin for electrical contact with a complementary spring probe pin and complementary contact pad, respectively, in the complementary connector; a ground body including a ground base (86, 86') that is electrically conductive having a thickness extending between a first ground base surface and a second, opposing ground base surface such that said thickness defines a plurality of apertures each of which receives one of the dielectric inserts (94, 94' 100) for placing each first insert surface in a confronting relationship with the complementary connector and a predetermined characteristic electrical transmission line impedance is exhibited for each electrical contact (110, 114) based on the configuration of each dielectric insert (94, 94', 100) in relation to the ground base (86, 86'); and a circuit board arrangement (154, 156, 164, 154', 156', 164') having a first interface end and an external, opposing interface end with the first interface end electrically interfacing each electrical contact (110, 114) proximate to the second insert surface of each dielectric insert (94, 94' 100) and including at least one ground path in electrical communication with the ground body and extending from the first interface end of the circuit board arrangement (154, 156, 164, 154', 156', 164') to the external interface end for grounding the ground body, and the circuit board arrangement (154, 156, 164, 154', 156', 164') forms a plurality of high speed data paths (200a - 200f, 200a'-200g'), associated with said electrical contacts (110, 114), to form differential pairs configured each to exhibit a predetermined differential impedance as said characteristic electrical transmission line impedance along each high speed data path (200a - 200f, 200a' - 200g') and extending to the external interface end of the circuit board arrangement (154, 156, 164, 154', 156', 164') such that each high speed data path (200a - 200f, 200 a' - 200g') serves as an independent transmission line structure that provides a data transfer rate of at least 1 gigabit per second. a plurality of dielectric inserts (94, 94' 100) each of which supports one or more electrical contacts (110, 114) for access by the complementary connector at a first insert surface of each dielectric insert (94, 94' 100) and each of the dielectric inserts (94, 94' 100) defines an opposing, second insert surface and each electrical contact (110, 114) is selected as one of a contact pad and a spring probe pin for electrical contact with a complementary spring probe pin and complementary contact pad, respectively, in the complementary connector; a ground body including a ground base (86, 86') that is electrically conductive having a thickness extending between a first ground base surface and a second, opposing ground base surface such that said thickness defines a plurality of apertures each of which receives one of the dielectric inserts (94, 94' 100) for placing each first insert surface in a confronting relationship with the complementary connector and a predetermined characteristic electrical transmission line impedance is exhibited for each electrical contact (110, 114) based on the configuration of each dielectric insert (94, 94', 100) in relation to the ground base (86, 86'); and a circuit board arrangement (154, 156, 164, 154', 156', 164') having a first interface end and an external, opposing interface end with the first interface end electrically interfacing each electrical contact (110, 114) proximate to the second insert surface of each dielectric insert (94, 94' 100) and including at least one ground path in electrical communication with the ground body and extending from the first interface end of the circuit board arrangement (154, 156, 164, 154', 156', 164') to the external interface end for grounding the ground body, and the circuit board arrangement (154, 156, 164, 154', 156', 164') forms a plurality of high speed data paths (200a - 200f, 200a'-200g'), associated with said electrical contacts (110, 114), to form differential pairs configured each to exhibit a predetermined differential impedance as said characteristic electrical transmission line impedance along each high speed data path (200a - 200f, 200a' - 200g') and extending to the external interface end of the circuit board arrangement (154, 156, 164, 154', 156', 164') such that each high speed data path (200a - 200f, 200 a' - 200g') serves as an independent transmission line structure that provides a data transfer rate of at least 1 gigabit per second.