A flexible duct includes a hollow tube shape, at least one end, a first circumferential attachment and a second circumferential attachment integral to the at least one end, wherein the first circumferential attachment and the second circumferential attachment are each configured to independently mechanically couple the at least one end around a first inlet or a first outlet, and wherein the first circumferential attachment and the second circumferential attachment are different. A method includes providing a flexible duct, selecting one of the first circumferential attachment or second circumferential attachment of the flexible duct, and mechanically coupling the selected first circumferential attachment or second circumferential attachment around the first inlet or first outlet. A connector for a flexible duct includes a hollow tube shape extending between a first connector end and a second connector end and a first circumferential attachment and second circumferential attachment integral to the at least one end.