Fire Damper, Fire Damper, Square, Mounting Type Static, Horizontal, Nominal Duct Width 24 in, Nominal Duct Height 24 in, Damper Depth 3 11/16 in, Material 22 ga Galvanized Steel, Damper Height 23 3/4 in, Damper Width 23 3/4 in, Recommended Retaining Angle 2TGJ1, Fire Rated 1 1/2 hr, Free Area 3.068 sq ft, Fusible Link 165 Degrees F, For Use With Low Pressure HVAC Systems, Standards UL Standard 555, NFPA 80, 90A and 101, IBC, CSFM, NYC MEA, Includes Stainless Steel Closure Spring, UL Fusible Link