a retaining ring disposed inside the side wall the side wall and the retaining ring define a gap extending around the shell the cushion has a side wall with an outer peripheral edge portion including a tongue extending around the cushion the tongue of the cushion is received in the gap in the shell to secure the cushion to the shell various straps assemblies and forehead adjusters for nasal masks are also shown application_number US 60172903 A description the present invention relates to a nasal mask the invention is applicable to masks of differing constructions as representative of the invention fig1 and 2 illustrate a nasal mask 10 constructed in accordance with a first embodiment of the invention the mask 10 includes a shell 20 a forehead support assembly 30 extends upward from the shell 20 a face cushion 40 is supported on the shell 20 the mask 10 also includes headgear 80 connected with the forehead support assembly 30 and with the shell 20 for helping to hold the mask on the user 39 s head the shell 20 is preferably made of a rigid plastic material which is preferably optically transparent and impermeable to gas or air the shell 20 has a rounded triangular configuration when viewed from the front being narrower on top by the nasal bridge region and wider by the base of the nose the shell 20 includes.