Fire Damper Fire Damper Round Mounting Type Dynamic Vertical or Horizontal Nominal Duct Dia 4 in Damper Depth 13 5/8 in Material 20 ga Galvanized Steel Damper Dia 3 7/8 in Fire Rated 1 1/2 hr Free Area 0.064 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