A seal assembly (400) is used with a slide-out room in a mobile living quarters. The seal assembly (400) includes three sealing lips (402) which are adapted to abut a top phalange (406) of a slide-out room when the room is a retracted position. The sigma seal (400) includes a pair of opposing concave walls 404 which are adapted to collapse when the slide-out room is in a retracted position. The sigma seal (400) is further adapted to be secured to a wall or a static surface (410) of a mobile living quarters.