The Model 3EF3HD Expandable Flex Connector is designed for use with gas-fired appliances equipped with draft hoods and other appliances listed for use with Type B Gas Vent. Single Wall Expandable-Flexible Gas Vent Connector (EFC) offers a simple connection between appliance and Type B vent. UL listed and only requires 1 in. minimum airspace clearance to combustibles and has multiple applications, can be for single vent or combined vent. Features: Flexible connector is designed to simplify connections between a gas fired appliance and rigid type B gas vent No elbows are required for installation Expands 1 ft. to 3 ft. Limited lifetime warranty Integrated draft hood connector Provides 360 degrees flexibility Connects to AmeriVent style B-vent Connects to 3 in. rigid B-vent and appliance collar Allow 1 in. clearance for combustibles Double-Wall design