Gaskets

A gasket comprising a generally planar supporting sheet, the supporting sheet having a trough formed therein, the trough opening through upper surface of the sheet and having a substantially constant transverse cross-section, the trough extending around a continuous closed path around an opening through the gasket, the gasket also comprising an elongated bead made of resilient material and having a substantially constant transverse cross-section, the bead being mounted in said trough and extending around said path, the bead comprising a projection which, in an uncompressed state of the bead, projects out of the trough beyond the upper surface of the sheet so that the projection can be compressed to form a continuous seal along said path, wherein said bead has a transverse cross-section defined by lower and side surfaces which conform to and engage bounding surfaces of the trough, and also defined by an upper surface which, in an uncompressed state of the bead, defines said projection and a recess extending parallel to said projection, the recess being formed within said trough, said projection being positioned on one side of the longitudinal centre-line of the bead and said recess being positioned on the other side of said centre-line, the projection having a side surface which is continuous with a side surface and with the bottom of the recess, the projection and the recess both being dome-shaped.