Z-Flex Z-Vent 3" Universal Adaptor: Modine, Nordyne, QuietSide (2SVSNA03.5),Z-Flex" /> 3" Universal Adaptor: Modine, Nordyne, QuietSide Has seals on both ends (female on both ends) Connects the tankless water heater to the 3" Z-Flex Z-Vent Stainless Steel Venting Rated AL29-4C and is approved for Category I (vertical only), II, III & IV applications