A mask for supplying gas under pressure to the nasal airway of a human includes a series of flexible stretchable straps formed from an elastomeric material for locating the mask against the human face. The straps are integrally formed or joined to define a perimeter enclosing an aperture adapted to fit around the nasal area of a human. The straps are configured to approximate to the three dimensional shape of the region around the nasal area of the human face as they arm stretched, to form a tight fitting seal. The mask may be used with or without a manifold.