The present invention relates to a cushion (10) for a patient interface that delivers breathable gas to a patient, the cushion comprising: a base wall (28) structured to be connected to a frame； and a membrane (32) adapted to form a continuous seal on the patient's face, wherein at least a portion of the base wall includes a tapered portion that tapers towards the membrane； wherein the base wall defines a spring constant that varies along a length of the seal； wherein the membrane forms an elongated ridge (35) in a nasal bridge region (16), the elongated ridge having sloping sides (36) that meet to form an elongated crest (38)； and wherein the elongated ridge is structured to invert its configuration upon engagement with the patient's nasal bridge region and a leading edge (46) of the elongated ridge is adapted to roll as the elongated ridge inverts its configuration.
