A connector assembly, comprising: first and second releasably mateable connector units (12,14) each having a rear end, a front end, and a longitudinal axis, and each connector unit comprising a shell, a manifold located at least partially inside the shell, at least one contact chamber (15,16) containing at least one contact, each manifold having a front end wall with at least one inlet communicating with the contact chamber and aligned with the contact, the shell and manifold of each connector unit being relatively movable; the front end wall of each manifold having at least one recessed seat having opposite first and second ends; at least one rolling seal movably mounted in each recessed seat, the rolling seal having at least one through bore; each rolling seal being movable relative to the respective seat in a non-axial direction relative to the respective connector unit between a sealed and closed condition in which the through bore is offset from the respective inlet and the inlet is sealed when the connector units (12,14) are unmated and an open condition in which the through bore is aligned with the respective inlet when the connector units (12,14) are mated to allow the contact of at least one connector unit to extend through the inlet into engagement with the contact of the other connector unit; the manifold of the second connector unit being retractable in a rearward direction relative to the respective shell and the shell of the first connector unit being retractable in a rearward direction relative to the respective manifold during mating of the connector units (12,14), whereby a forward portion of the manifold of the first connector unit enters the shell of the second connector unit on mating; and the shell of the second connector unit having inwardly facing cam formations (126,128) and each rolling seal having at least one outwardly directed, eccentric rotator (59,60) configured for engagement with a respective cam formation on mating and de-mating of the connector units (12,14), whereby travel of the respective rotators along the respective cam formations (126,128) during mating and de-mating rotates the rolling seals of both connector units (12,14) into the open and closed positions, respectively. first and second releasably mateable connector units (12,14) each having a rear end, a front end, and a longitudinal axis, and each connector unit comprising a shell, a manifold located at least partially inside the shell, at least one contact chamber (15,16) containing at least one contact, each manifold having a front end wall with at least one inlet communicating with the contact chamber and aligned with the contact, the shell and manifold of each connector unit being relatively movable; the front end wall of each manifold having at least one recessed seat having opposite first and second ends; at least one rolling seal movably mounted in each recessed seat, the rolling seal having at least one through bore; each rolling seal being movable relative to the respective seat in a non-axial direction relative to the respective connector unit between a sealed and closed condition in which the through bore is offset from the respective inlet and the inlet is sealed when the connector units (12,14) are unmated and an open condition in which the through bore is aligned with the respective inlet when the connector units (12,14) are mated to allow the contact of at least one connector unit to extend through the inlet into engagement with the contact of the other connector unit; the manifold of the second connector unit being retractable in a rearward direction relative to the respective shell and the shell of the first connector unit being retractable in a rearward direction relative to the respective manifold during mating of the connector units (12,14), whereby a forward portion of the manifold of the first connector unit enters the shell of the second connector unit on mating; and the shell of the second connector unit having inwardly facing cam formations (126,128) and each rolling seal having at least one outwardly directed, eccentric rotator (59,60) configured for engagement with a respective cam formation on mating and de-mating of the connector units (12,14), whereby travel of the respective rotators along the respective cam formations (126,128) during mating and de-mating rotates the rolling seals of both connector units (12,14) into the open and closed positions, respectively.