Sure-Vent Air Admittance Valve. Provides the ideal venting solution for island sinks, remote bathrooms, and remodel jobs by eliminating the need for a stack vent. Designed to block sewer gases in DWV systems by opening and closing when the slightest change in pressure is detected. Available with PVC or ABS adapters. Vents up to 20 DFU (branch) or 8 DFU (stack) and fit 1-1/2 In. pipes.