A seal member for an interface assembly, the seal member comprising: a sidewall (134)； a flange (110) extending inwardly from the sidewall (134), the flange comprising a face contacting surface, the face contacting surface comprising an edge (112) that at least partially defines an opening； and a first and a second thickened panel (130), wherein the first and second thickened panels comprise locally thickened regions of at least the flange, each of the thickened panels having a first side at or proximate to a respective portion of the edge, and arranged so as to increase the lateral pressure against a lateral nose surface of a user, in use.
