Abstract: A zipper assembly is used to releasably attach a bag liner to a sleeping bag to retain the bag liner within the sleeping bag and to expand the bag interior to compensate for volume lost by insertion of the bag liner. The zipper assembly includes first and second pairs of spaced rows of liner zipper teeth. Two rows are secured to the existing rows of bag zipper teeth by two zipper slides. A third zipper slide releasably secures two of the other rows of liner zipper teeth to permit an individual to enter and exit the bag liner. In another embodiment of the invention, a protective cover is releasably secured to a bag by a zipper assembly.