A tubular prosthesis is provided which includes a tubular member and an outer covering sealed to portions of the tubular member, with a pocket being defined therebetween. A filling agent, preferably a substantially incompressible agent, is disposed in the pocket so as to cause portions of the outer covering to expand from the tubular member. As an endovascular prosthesis, the filled pocket can be used as a seal against the wall of a blood vessel to prevent Type I endoleaks.