A mask for supplying gas under pressure to an airway of a human including a flexible manifold shell, an air inlet connected to an air delivery pipe, and at least two side walls which are at least partially formed by portions of the manifold shell. A flexible face contacting element defines an orifice to accommodate the nose of the human. Straps connected to the mask allow forces exerted by the straps to deform the manifold shell at least along X and Y axes, creating a variety of different orifice shapes. The face contacting part includes a flexible membrane allowing X and Y axis movement of the mask and movement of the mask along a Z axis between the users face and the manifold shell. The flexible membrane may deform while retaining a gas seal against the face of a wearer.
