US Patent 7861715 Mask system

A mask system for treating sleep disordered breathing, comprising headgear, a shell/cushion including a channel adjacent a front aperture, a frame, an elbow including at least one undercut on a proximal end, a retaining ring including a rear flange adapted to be retainably insertable in the channel of the shell/cushion, and a front flange adapted to retainably engage with the at least one undercut of the elbow.