Abstract: A connector (10) for sealing an elongated tube (14) to a body (22) comprises a nut (12) concentrically about the tube (14) proximate the flared end (16). The nut (12) has a threaded exterior portion (34) and an abutting face (42) proximate to and concentric with the exterior face (32) of the flared end (16). A non-linear spring (44) between the exterior face (32) of the flared end (16) and the abutting face(42) of the nut (12), and is displaced upon tightening of the nut (12) to the body (22) to generate a substantially constant restorative force over a portion of the displacement to urge the interior face (30) of the flared end (16) into sealing engagement with and against the shoulder (38) of the body (22).