A nasal prong for a cushion member for use with a patient interface device that includes a casing, a flap extending from the casing for insertion into a nostril of a patient, and a bottom cap. The casing and the bottom cap define a space. A fill material is disposed in the space defined by the casing and the bottom cap, wherein the casing is structured to deform and conform to a shape of a portion of the nostril when the nostril applies pressure to the casing.