A ring-shaped interfacial seal for a connector assembly includes an internal radial surface, inward oriented, surrounding a sealing surface of a connector, an external radial surface, outward oriented, surrounded by a second sealing surface, opposed top and bottom surfaces, and a groove in the bottom surface. The groove receives a sealing ring of a second connector. An internal sealing portion of the seal, located between the groove and the internal surface, and/or an external sealing portion of the seal, located between the groove and the external surface, is compressed radially.