a nasal mask of the type for delivering gas for example to ease or assist the breathing process includes a shell and a cushion connected with the shell . the shell has a side wall and 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 .