An endovascular prosthesis includes a tubular body and a flexible springy mobile external coupling. The tubular body includes a graft material and stents coupled thereto with a forms a lumen therethrough. The mobile external coupling extends outwardly from the tubular body. The mobile external coupling includes a graft material and is generally frustoconically shaped. The mobile external coupling includes a base coupled to the tubular body, a top spaced from the tubular body, and a coupling lumen disposed between the base and the top, wherein the coupling lumen is in flow communication with the body lumen. A helically shaped stent may be coupled to the coupling graft material to make it flexible and springy.
