An electrical penetrator (10, 100, 140), comprising: an insulating housing of non-conductive material having a through bore and opposite first and second ends; a first, elongate electrical conductor (16,128,142,164) extending through at least part of the length of the through bore and having a first end outside a first end of the insulating housing and a second end; a second electrical conductor (18, 126, 146, 166) having a first end and a second end, at least the second end of the second electrical conductor being located outside the second end of the insulating housing; the second end of the first electrical conductor (116,128,142,164) being in electrical communication with the first end of the second electrical conductor (18, 126, 146, 166), and at least one of the conductors being movable relative to the other conductor while maintaining electrical communication between the conductors; the insulating housing and the first electrical conductor (16,128,142,164) having first abutting outer surface portions (124, 123) of corresponding diameter at the first end of the insulating housing; the insulating housing and second electrical conductor (18, 126, 146, 166) having second abutting outer surface portions (124, 123) of corresponding diameter at the second end of the insulating housing; a first hermetic seal of conductive material extending between the first end of the insulating housing and the first electrical conductor and a second hermetic seal of conductive material extending between the second end of the insulating housing and the second electrical conductor; the first and second hermetic seals comprising first and second cylindrical sleeves (122, 134, 147), the first cylindrical sleeve secured over the first abutting outer surface portions (123, 124) of the insulating housing and first conductor and the second cylindrical sleeve secured over the second abutting outer surface portions of the insulating housing and second conductor, the first and second conductors having an outer surface substantially flush with adjacent outer surface portions of the insulating housing and first and second conductor, respectively; wherein each cylindrical sleeve (122, 134, 147) is a metal sleeve brazed to the outer surface portion of the respective end of the insulating housing and brazed or welded to the outer surface portion of the respective electrical conductor. an insulating housing of non-conductive material having a through bore and opposite first and second ends; a first, elongate electrical conductor (16,128,142,164) extending through at least part of the length of the through bore and having a first end outside a first end of the insulating housing and a second end; a second electrical conductor (18, 126, 146, 166) having a first end and a second end, at least the second end of the second electrical conductor being located outside the second end of the insulating housing; the second end of the first electrical conductor (116,128,142,164) being in electrical communication with the first end of the second electrical conductor (18, 126, 146, 166), and at least one of the conductors being movable relative to the other conductor while maintaining electrical communication between the conductors; the insulating housing and the first electrical conductor (16,128,142,164) having first abutting outer surface portions (124, 123) of corresponding diameter at the first end of the insulating housing; the insulating housing and second electrical conductor (18, 126, 146, 166) having second abutting outer surface portions (124, 123) of corresponding diameter at the second end of the insulating housing; a first hermetic seal of conductive material extending between the first end of the insulating housing and the first electrical conductor and a second hermetic seal of conductive material extending between the second end of the insulating housing and the second electrical conductor; the first and second hermetic seals comprising first and second cylindrical sleeves (122, 134, 147), the first cylindrical sleeve secured over the first abutting outer surface portions (123, 124) of the insulating housing and first conductor and the second cylindrical sleeve secured over the second abutting outer surface portions of the insulating housing and second conductor, the first and second conductors having an outer surface substantially flush with adjacent outer surface portions of the insulating housing and first and second conductor, respectively; wherein each cylindrical sleeve (122, 134, 147) is a metal sleeve brazed to the outer surface portion of the respective end of the insulating housing and brazed or welded to the outer surface portion of the respective electrical conductor.