Studor 20349 REDI-VENT Air Admittance Valve, 1-1/2" or 2" ABS Adapter, White The unique design of the Studor REDI-VENT provides ventilation to prevent the loss of water seals in traps without the need for expensive roof penetration and vent piping For venting single fixtures, kitchen sinks and bathroom groups including back to back applications up to 20 DFUS Fits 1 " and 2" pipe sizes ANSI/ASSE 1051, ANSI/ASSE 1050, NSF 14, Warnock Hersey, ICC-ES PMG-1025, C-IAPMO Simplify drainage and waste venting with the Studor REDI-VENT Air Admittance Valve