Plumbing Z-FLEX Venting | 4″ Z-Vent Universal Appliance Adapter W/ Backflow

4″ Universal Appliance Adaptor With Back-Flow Preventer For: Takagi, Paloma, Rheem, Noritz Tankless Water Heaters. This Universal Adaptor Has Seals On Both Ends And Has A Back-Flow Preventer Built In. Useful In Colder Climates To Prevent Cold Air From Flowing Back Into Your Heat Exchanger. Universal Adaptor Connects Tankless Water Heater To The 4 Z-Flex Z-Vent Stainless Steel Venting