Oatey® 2" – 3" 160 DFU Sure-Vent AAV 2" x 3" Sch. 40 PVC adapterOatey Sure Vent 160 DFU Capacity Air Admittance Valve's one way valve is designed to allow air to enter the plumbing drainage system when negative pressures develop in the piping system. Complies to ASSE Standard 1050 and 1051 For use as a secondary vent One size approved to handle up to 4" vent pipe Opens closes as needed by building's plumbing system