An expandable seal features a ring structure with internal and external seal. The seals are mounted in grooves and extend beyond a base outer dimension on the ring on the inside and the outside surfaces. Bumps are positioned in axial alignment with the seals but in opposition to each seal so that the exterior seal has a bump axially aligned but on the inside of the ring and the inner seal has a bump axially aligned and on the outside surface of said ring. The bumps have end transitions to the base dimension to create a volume for the seal material to travel axially when radially expanded from a mandrel extending within for effective seal containment. Seal rings can be stacked to adjust to dimensional irregularities in the surrounding tubular or the mandrel and to back each other up in the event of seal failure in any one seal ring.