<p>A rupture disk to be sealingly engaged with a pressurized system is disclosed. The rupture disk includes an annular flange and a rupturable portion. The rupturable portion has a domed shape with a convex surface and a corresponding concave surface and a structural apex formation disposed at the apex of the dome. The structural apex formation includes a crease that is formed in at least one of the concave and convex surfaces.</p>
