A supplementary cooling element (102; 103; 311; 611) for use in conjunction with a primary cooling element, the supplementary cooling element comprising: a first component (201; 301; 501; 601; 701) containing a passage (224; 324; 511; 711) into which a fluid is circulated for the purposes of removing heat, wherein the first component has a tapered profile (211; 313); a second component (202; 302; 505; 602; 705, 706) defining a passage sized to receive the first component, the second component having exterior dimension arranged for being received within an aperture (101; 110) in the primary cooling element, the aperture having an interior wall; a biasing element (206; 306; 507; 606; 707) configured to exert a force on one of the first component and the second component to force movement relative to the other of the first component and the second component to, thereby, create a change in the exterior dimension of the second component, thereby causing: a thermally conductive pressure connection to be formed between the first component and the second component; and a thermally conductive pressure connection to be formed between the second component and the interior wall of the aperture in the primary cooling element, wherein: the movement of the first component within the second component causes the second component to expand outwardly; or the movement of the second component along an exterior surface of the first component causes the second component to expand outwardly. a first component (201; 301; 501; 601; 701) containing a passage (224; 324; 511; 711) into which a fluid is circulated for the purposes of removing heat, wherein the first component has a tapered profile (211; 313); a second component (202; 302; 505; 602; 705, 706) defining a passage sized to receive the first component, the second component having exterior dimension arranged for being received within an aperture (101; 110) in the primary cooling element, the aperture having an interior wall; a biasing element (206; 306; 507; 606; 707) configured to exert a force on one of the first component and the second component to force movement relative to the other of the first component and the second component to, thereby, create a change in the exterior dimension of the second component, thereby causing: a thermally conductive pressure connection to be formed between the first component and the second component; and a thermally conductive pressure connection to be formed between the second component and the interior wall of the aperture in the primary cooling element, a thermally conductive pressure connection to be formed between the first component and the second component; and a thermally conductive pressure connection to be formed between the second component and the interior wall of the aperture in the primary cooling element, wherein: the movement of the first component within the second component causes the second component to expand outwardly; or the movement of the second component along an exterior surface of the first component causes the second component to expand outwardly. the movement of the first component within the second component causes the second component to expand outwardly; or the movement of the second component along an exterior surface of the first component causes the second component to expand outwardly.