A facial mask assembly for covering at least the nose and nares of a patient's face and compensating for any unequal forces that may be generated in the straps holding the mask on the patient's face. The assembly includes a rigid, cup-shaped shell with a soft seal engaging and sealing against the patient's face. The shell is preferably secured or attached to the patient's head by an arrangement including a rigid plate mounted to the rigid shell and a harness. The harness extends about the back of the patient's head and preferably has side straps attached to the top of the rigid plate. The rigid plate is loosely mounted to the rigid shell at at least three locations and can move to compensate for any unequally applied forces that would otherwise tend to rock or cock the shell off the patient's face and create a gap or leak in the seal. The invention also includes a modified hose coupling that permits the rigid shell and the flexible hose connected to the respiratory device to rotate relative to each other about multiple axes.