Disk (flat ring) caskets are commonly employed in conjunction with the ConFlat (R) metal sealing system. The use of the disk gasket, however, limits the seal performance on the ConFlat system because considerable tightening force is wasted in the sealing process when the flange knife edge cleaves the surfaces of the disk gasket. The taper-seal type gasket, which seals entirely by the compression of its corners without surface shearing, can be expected to improve the inefficiency of the ConFlat system relative to performance using conventional disk gaskets. Tightening tests on both gasket versions demonstrated that the seal area on the taper-seal type gasket was some 1.6-3.7 times larger than that on conventional disk gaskets, even when the taper-seal type gasket material is relatively hard. This result suggests that the tightening force acts more effectively to form a sealed area on a taper-seal gasket than a disk gasket. The two types of gaskets also differed in their stress distributions under the tightening load. Results of stress analyses using computer simulation showed that the stress concentration occurred in the conventional disk gasket around the tip of flange knife edge, and that maximum stress could be over four times larger than that seen in the taper-seal gasket. This excessively high stress in the disk gasket prevented achievement of a wide seal area, and intensified the creep of gasket materials during the baking process, this increasing the probability of leaks developing. The characteristic mode of deformation of the taper-seal gasket generates a highly stable stress distribution, virtually independent of the tightening torque; thus, good seal performance is realized, even under sever thermal cycling conditions.