A cushion assembly for a patient interface for sealed delivery of a flow of air at a continuously positive pressure with respect to ambient air pressure to an entrance to the patient's airways including at least entrance of a patient's nares, wherein the patient interface is configured to maintain a therapy pressure in a range of about 4 cmH20 to about 30 cmH20 above ambient air pressure in use, throughout the patient's respiratory cycle, while the patient is sleeping, to ameliorate sleep disordered breathing, the cushion assembly comprising: an elastomeric support portion ; an elastomeric seal-forming structure supported by the elastomeric support portion , the elastomeric seal-forming structure being shaped to be bisected by a sagittal plane that includes a line tangent to the elastomeric seal-forming structure at a superior tangent point and at an inferior tangent point , the elastomeric support portion being more rigid than the elastomeric seal-forming structure , the elastomeric seal-forming structure comprising a first compliant region that includes the superior tangent point and a second compliant region separated from the first compliant region by a support region that is more rigid than the first and second compliant regions (3175A; D, 6010A; C); a tie forming a continuous structure with a sealing surface of the seal-forming structure and being anchored to the elastomeric support portion ; and a plenum chamber configured to receive the positive pressure air, the plenum chamber being defined by the elastomeric support portion and the elastomeric seal-forming structure , wherein the cross-sectional shape of the cushion assembly at the tie is a closed loop, wherein the cross-sectional shape of the cushion assembly at all other portions of the elastomeric seal-forming structure is open, wherein the more rigid support region extends to and is anchored by the elastomeric support portion , and wherein an elastomeric wall thickness in the more rigid support region is invariable, and wherein the elastomeric seal-forming structure comprises an inner surface forming a boundary for the chamber and comprises an outer surface opposite the inner surface. an elastomeric support portion ; an elastomeric seal-forming structure supported by the elastomeric support portion , the elastomeric seal-forming structure being shaped to be bisected by a sagittal plane that includes a line tangent to the elastomeric seal-forming structure at a superior tangent point and at an inferior tangent point , the elastomeric support portion being more rigid than the elastomeric seal-forming structure , the elastomeric seal-forming structure comprising a first compliant region that includes the superior tangent point and a second compliant region separated from the first compliant region by a support region that is more rigid than the first and second compliant regions (3175A; D, 6010A; C); a tie forming a continuous structure with a sealing surface of the seal-forming structure and being anchored to the elastomeric support portion ; and a plenum chamber configured to receive the positive pressure air, the plenum chamber being defined by the elastomeric support portion and the elastomeric seal-forming structure , wherein the cross-sectional shape of the cushion assembly at the tie is a closed loop, wherein the cross-sectional shape of the cushion assembly at all other portions of the elastomeric seal-forming structure is open, wherein the more rigid support region extends to and is anchored by the elastomeric support portion , and wherein an elastomeric wall thickness in the more rigid support region is invariable, and wherein the elastomeric seal-forming structure comprises an inner surface forming a boundary for the chamber and comprises an outer surface opposite the inner surface. <EOS>