Duct-Seal 321 is a GREENGUARD Gold-certified, all-purpose, industrial-grade duct sealant for all types of metal duct, fiberglass duct board, duct fabric, and flex duct. It includes UV inhibitors for extended outdoor exposure and built-in fiber reinforcement for added strength. This non-toxic water-based product is solvent free and is suitable for residential use

Water-based, smooth, fiber-reinforced, UL181B-M, up to 20" w.c., enhanced mold/mildew properties, enhanced UV resistance.