A single-ply sheet metal seal ring with a convoluted, V/E-shaped cross-section having planar-circumferential flexibility is shown to be more capable of conforming to the sealing face contours of warped, weld-deformed flanges than thin layer, multiple-ply seals developed to replace earlier E-shaped seals for this purpose. The basis of the improved flexibility of the new seal lies mainly in the discovery of geometric relationships that permit a reduction in the thickness of the sheet material employed in the construction of the seal while maintaining its pressure containing capabilities.