A medical filler delivery assembly includes a micro catheter for delivering filler material such as filamentary material into an aneurysm in a vessel, the assembly also including a positioning mechanism which includes a support element made of knitted wires, as well as an expansion mechanism for expanding the support element within the vessel. The wires form an array of polygonal, preferably rhomboidal cells, the wires being intertwined at their junctions by at least one turn around one another, the intertwined regions extending in the longitudinal direction of the support element. The support element is able to trap the micro catheter in position and in practice such that its distal end is disposed within the aneurysm sac.