number ECAP321 PVC Flue Pipe Rooftop Vent Cap The patented new flue cap is designed to improve air flow and eliminate excessive moisture and debris that can rust or damage high efficiency gas furnaces, tankless hot water tanks, plumbing or other PVC vented installations. For Use on all PVC-vented high efficiency applications: HVAC exhaust and intake, plumbing, gas venting and high efficiency tankless water heaters. Superior design, function and price to conventional concentric vents. Resistant to heat, cold, precipitation or UV radiation Protects furnace motor and interior from moisture, debris, and pests. Promotes unrestricted air flow of both Intake, and Vent flue OEM approved by A-mana, B-osch and G-oodman for use in 90% AFUE heating applications Precisely fits 1", 2", and 3" PVC pipe.