Fire Damper, Round, Mounting Type Dynamic, Vertical or Horizontal, Nominal Duct Dia. 6 In.Damper Depth 13-5/8 In.Material 20 ga. Galvanized Steel, Damper Dia. 5-7/8 In.Fire Rated 1-1/2 hr., Free Area 0.16 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 Life Safety DampersFire DampersAccommodate airflow in either direction.UL, NFPA, IBC, MEA, CSFMFire-resistance rating: 1-1/2 hr. Max. temp.: 165 F Curtain blade style NFPA 80 requires retaining angles