Gaskets that are primarily non-metal but which include a metal core and a secondary sealing ring for added sealing integrity in the event of a fire for insulating and general sealing applications, namely, for flange isolation in conjunction with cathodic protection, for isolation between dissimilar metals to prevent galvanic corrosion, for wellhead isolation from inter-connected flowlines, for mating mismatched ring-joint to raised-face flanges, for eliminating fluid trap corrosion between ring-joint flanges, for eliminating turbulence and flow-induced erosion between ring-joint flanges, for protecting against coating impingement on coated flange faces, and for sealing between flanges subjected to vibration/cavitation