The unique design of the Studor Mini-Vent provides plumbing ventilation to prevent the loss of water seals in traps without the need for costly roof penetration and vent piping. Studor Mini-Vent Air Admittance Valve with ABS Adapter is a one way valve used for branch or single fixture ventilation. It protects the water trap seals and does not allow sewer gases and smells to leak into the living space. When a negative pressure in the drainage pipe occurs, the valve opens to allow the entrance of air. When the pressure is balanced the Mini-Vent closes absolutely tight, so the foul air cannot escape. Fits: 1-1/2 or 2-inch x 2.625-inch vent height x 2-inch vent diameter. ABS construction with a temperature rating of -40 to 150 deg F.