A cushion assembly (3800, 6000) 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 (3100, 6010) supported by the elastomeric support portion, the elastomeric seal-forming structure (3100, 6010) 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 (3100, 6010), the elastomeric seal-forming structure comprising a first compliant region (3175A, 6010A) that includes the superior tangent point and a second compliant region (3175D, 6010C) separated from the first compliant region (3175A, 6010A) by a support region (3175C, 6010B) 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 (3100, 6010) 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 (3100, 6010), wherein the cross-sectional shape of the cushion assembly (3800, 6000) at the tie is a closed loop, wherein the cross-sectional shape of the cushion assembly (3800, 6000) at all other portions of the elastomeric seal-forming structure (3100, 6010) is open, wherein the more rigid support region (3175C, 6010B) extends to and is anchored by the elastomeric support portion, and wherein an elastomeric wall thickness in the more rigid support region (3175C, 6010B) is invariable, and wherein the elastomeric seal-forming structure (3100, 6010) 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 (3100, 6010) supported by the elastomeric support portion, the elastomeric seal-forming structure (3100, 6010) 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 (3100, 6010), the elastomeric seal-forming structure comprising a first compliant region (3175A, 6010A) that includes the superior tangent point and a second compliant region (3175D, 6010C) separated from the first compliant region (3175A, 6010A) by a support region (3175C, 6010B) 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 (3100, 6010) 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 (3100, 6010), wherein the cross-sectional shape of the cushion assembly (3800, 6000) at the tie is a closed loop, wherein the cross-sectional shape of the cushion assembly (3800, 6000) at all other portions of the elastomeric seal-forming structure (3100, 6010) is open, wherein the more rigid support region (3175C, 6010B) extends to and is anchored by the elastomeric support portion, and wherein an elastomeric wall thickness in the more rigid support region (3175C, 6010B) is invariable, and wherein the elastomeric seal-forming structure (3100, 6010) comprises an inner surface forming a boundary for the chamber and comprises an outer surface opposite the inner surface.