Abstract: A mold is described for the encapsulation of electrical components with a thermosetting resin composition, particularly components which have either no lead-out wires or such wires which are not suitable for locating the component within the mold. Fitted into opposing walls of the case of the mold are at least one pair of solid plugs of a flexible material, the plugs extending into the interior of the mold and being of a material which has a higher coefficient of cubic expansion than that of which the mold is constructed. The plugs are arranged to grip the component even though the mold walls expand outwards when the mold is heated to cure the thermosetting resin.