A patient interface device (8, 8′) for delivering a flow of breathing gas to an airway of a patient includes a grooved adjustment mechanism (20, 58, 78) having a main body (22, 60) formed from an elastic material, the main body having an outer surface having a plurality of convolutions (80) provided therein. Each convolution including a groove (24, 62, 84), and each convolution has a stiffness associated therewith. The stiffnesses associated with the convolutions increase from a first side of the main body to a second side of the main body.
