Oatey 1-1/2 In. to 2 In. Air Admittance PVC Vent Valve

20 DFU (Drainage Fixture Unit) capacity. Complies to ASSE (American Society of Safety Engineers) Standard 1050 and 1051 for use a a secondary vent. One size approved to handle up to 3" vent pipe. Opens and closes as needed by building's plumbing system, 1-1/2 - 2".