Fire Damper, Fire Damper, Square, Mounting Type Dynamic, Vertical or Horizontal, Nominal Duct Width 18 In., Nominal Duct Height 18 In., Damper Depth 3-11/16 In., Material 22 ga. Galvanized Steel, Damper Height 17-3/4 In., Damper Width 17-3/4 In., Recommended Retaining Angle 2TGH8, Fire Rated 1-1/2 hr., Free Area 1.640 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. This item has been restricted from sale in the following state(s): []