A device comprising a casing and having an initial configuration, an intermediate configuration, and a final configuration, wherein in the initial configuration the casing contains: a plurality of beads, a rupturable first container containing one or more isocyanates and a rupturable second container containing one or more polyols. In the final configuration the casing is substantially filled by a polyurethane in which the plurality of beads is embedded. In the intermediate configuration the device is transformed from the initial configuration to the final configuration by rupturing the first container and rupturing the second container so that the one or more isocyanates react with the one or more polyols in a reaction that forms the polyurethane. As the polyurethane is formed during the reaction the polyurethane surrounds the plurality of beads. The casing includes one or more vent tubes configured to allow gases formed by the reaction to escape the casing.