Abstract: Device for sealing an aperture, the device comprising liquid-in-polymer gel material (10) and means (11, 15) for forcing the gel material outwards into compression against an interior surface of the aperture in which the device is to be positioned in use, characterised in that a thin, flexible and preferably stretchable, coherent film (30, FIG. 4) of plastics material is positioned on (preferably adhered to) a surface of the gel material intended to seal against the said interior surface, preferably with a liquid component (30, FIG. 4) of the gel material in between the film and the interior surface.