Abstract: An improved fire barrier system is disclosed for interposition within an expansion joint between adjacent wall or floor members. In the disclosed embodiment, the invention is characterized in that the fire barrier system is symmetrical in both pairs of opposing quadrants defined by a first axis parallel to and midway between said mutually facing walls and transverse to said direction of elongation and a second axis transverse to said first axis and to said direction of elongation. This symmetry affords equal resistance to fire from either side of the barrier, eliminates the possibility of the joint being installed backwards, and permits the barrier system to be fire-rated for resistance to fire from either side of the barrier on the basis of a single test.