A cushion assembly for use with a respiratory mask includes a bladder filled with the combination of a gel (740) having a first indentation hardness and a gel (750) having a second indentation hardness. A seal forming structure is formed in one piece with the cushioning structure. The seal forming structure includes a thin membrane flap that is structured to provide a seal to the patient's face. The thin membrane flap includes a free end that is spaced from the cushioning structure in its substantially relaxed, unstressed state and is adapted to be responsive to a difference between mask pressure and ambient pressure to effect a seal with a face region of a patient.
