A patient interface for delivery of a supply of pressurised air or breathable gas to an entrance of a patient's airways including: a cushion member that includes a face contacting portion, a retaining structure and a resiliently flexible lip; and a frame member, wherein the retaining structure and the frame member are repeatedly engageable with and disengageable from one another, wherein a gas chamber is formed at least in part by engagement of the cushion member and the frame member, and wherein the resiliently flexible lip is configured to provide a sealing force between the cushion member and the frame member.