Abstract: An annular expandable seal assembly is disclosed for being packed between inner and outer cylindrical walls. The seal assembly has an annular expandable elastomeric seal element, an annular non-elastomeric anti-extrusion element, and an arcual non-elastomeric anti-extrusion bridge element. The seal element has opposing inner and outer axial surfaces and opposing first and second radial surfaces. The anti-extrusion element is coaxially positioned at the first radial surface and has a toroidal gap. The bridge element is positioned between the seal element and the anti-extrusion element in alignment with the toroidal gap. The seal assembly is set by being expanded so that the inner and outer surfaces respectively sealingly contact the inner wall and the outer wall, the toroidal gap expands, and the anti-extrusion element and the bridge element contact the outer wall.