of the present invention shape memory polymers have a further interesting property when a shape memory polymer is formed into a particular shape at a higher temperature the polymer will u201c remember u201d this shape such that when the polymer is cooled and forced into another shape the polymer will assume its original shape upon heating to a temperature above the state transition temperature examples of shape memory polymers may for example be found in the u s pat nos 6 388 043 and 6 160 084 in the international application wo 2004 110315 is further described how an implantable stent which comprises first and second layers of at least partially amorphous polymers can assume a first shape at a first temperature and second shape at a second temperature the contents of these three documents are incorporated herein by reference returning now to fig1 a and b the retaining member 4 which is made from a shape memory polymer was originally formed into the large diameter shape illustrated in fig1 b and was then cooled and stretched to the smaller diameter configuration illustrated in fig1 a when the sealing device 1 being at a temperature below the transition temperature is positioned at a vessel wall the outer member 3 can easily slide along the retaining member 4 when the sealing device 1 and in.