Designed to drain condensation and other liquids (i.e. liquid detergents or foams during air-duct cleaning operations). Easy installation: just drill a hole and screw-in the drain fitting. All parts are protected against corrosion: nickel-plated brass or STST V4A (316)
Drain Fittings ST-K
With conical (small) washer for rectangular and round ducts. These plugs are often installed on kitchen hoods.