Abstract: A respiratory mask system includes a mask interface and a headgear assembly. The headgear assembly is adjustable and comprised of an elastic portion, a non-elastic portion and a restriction mechanism configured to provide a force resisting movement of the non-elastic portion when the elastic portion is extended. There is a support beam coupled to the non-elastic portion and extending along a portion of the headgear that is curved along its longitudinal extent. In this way particular seal modules can be comfortably fitted to a user and any blow off force is mitigated. A particular example of the respiratory mask system includes provision for removable attachment between the seal and a mask frame, the mask frame and a yoke of the headgear; and between a conduit and the mask frame.