A ferrule for coupling a tube to a fitting body of a fitting assembly. The ferrule may include a reduced thickness portion near a nut end of the ferrule, the reduced thickness portion being thinner than adjacent portions of the ferrule and configured to flex when the fitting assembly is made up. The ferrule may include a thin section toward the bite end of the ferrule, and an axially middle portion, between the thin section and the reduced thickness portion, may be configured to bow radially outwardly during assembly. The reduced thickness portion may have a radial thickness less than any other portion of the ferrule between the nut end and a bite edge of the ferrule closest to the nut end.