A seal for a duct having an upstream portion and a downstream portion, the duct upstream portion and the duct downstream portion separated by a first gap, includes a first portion having a length greater than a width of the first gap between the first portion and the second portion, the first portion having a first thickness, a first upstream end and a first downstream end; a second portion having a length greater than a width of the gap between the first portion and the second portion, the second portion having a second thickness, a second upstream end and a second downstream end; and an attachment between the first portion and the second portion such that the first portion and the second portion move relative to each other, wherein the first portion is inside the duct and the second portion is outside of the duct.