the balloon openings allowing it to be filled by inflation fluid and subsequently solidifying fluid the balloon 10 includes a plurality of pores 20 through which an aqueous inflation fluid can be perfused fig1 b shows the balloon of fig1 a after retraction of the guidewire in an inflated configuration the stiffening member 18 floats freely within the inflated balloon in an alternative embodiment not shown the stiffening member 18 may project inwardly into the balloon from the distal end 21 of the inflation lumen instead of balloon distal end 15 a guidewire exit valve may be mounted in the balloon wall at end 15 and exit valve 19 may optionally be removed in yet a further alternative embodiment member 18 is shortened and a second stiffening member is provided projecting inwardly from lumen end 21 is provided to contact the shortened member 18 when the guidewire is present to effect compressive stiffening in other alternative embodiments exit valve 19 may be moved to the distal end of the balloon or an intermediate location on member 18 fig2 6 illustrate various stages of a preferred process for filling and installation of a balloon 22 similar to balloon 10 except that the stiffening member is not present and a guidewire exit valve 23 is located on the distal end of the balloon to allow passage of the guidewire therethrough balloon 22 is shown in various stages after the balloon and catheter assembly has been delivered to an aneurysm 25 and the guidewire withdrawn the filling and installation process begins as shown in fig2 by filling the balloon with.