Abstract: A special type of flange ring (201) for making bolted flanged joints between axially consecutive component parts of hollow fabrications, such as gas turbine aero engine casings (210). Each flange joint face (206) has, at its radially inner circumference, a radially extending sealing land or flat (216), the remainder of the flange joint face comprising, when in the unstressed condition, a frustoconical surface (209) inclined at a small angle (c.degree.) to the radial plane (207) of the sealing flat (216). The frustoconical surface (209) is drawn into contact with a complementary joint surface (208) when the bolts (204) are tightened. The flange rear face (212) is parallel to the frustoconical surface (209). This configuration creates a joint having a large line reaction force along the sealing land (216), thereby providing efficient sealing against internal pressure even when tension forces in the casing (210) are present. Alternative embodiments are described.