The gel-filled cushion conforms around the nose and uses the SST flap to create a consistent seal all night. The gel technology allows for a greater variety of facial features such as facial hair. As an added benefit, the ComfortGel cushion can be boiled and molded for a custom fit. The boiling process softens the cushion and allows the gel to form around your unique face. Most people get a good fit from one of the four sizes without molding the gel.