An envelope gasket features a bonded construction. In one example, a virgin PTFE envelope is bonded to a pair of microcellular or expanded PTFE filler material annular rings. The PTFE filler annular rings are then bonded together around a corrugated metal insert ring (on the inner and outer diameter), thus sealing inside microcellular or expanded PTFE. Alternatively, when using expanded graphite filler material annular rings, the PTFE envelope is bonded to the expanded graphite filler rings by pressure and heat, and the filler rings are bonded to each other by pressure during the bonding process.