For use in sheet metal air ducts which penetrate ceilings of hourly-rated fire resistant assemblies.
UL 555C tested and listed (M557 Ceiling Design)
Frame: Roll Formed, 22 Ga. galvanized steel
Blades: 22 Ga. galvanized steel
Blade Insulation: Non-asbestos, ceramic blanket on blades
Spring: Corrosion resistant stainless steel spring
Finish: Mill galvanized