An annular mesh expandable radially from a compact diameter to a radially-expanded deployed disposition in which the mesh is capable of sustaining a radially outwardly directed resistive force even when flexing its longitudinal axis out of a straight line, the mesh being composed of stenting struts, the stenting struts being arranged in a plurality of zig-zag strings around the circumference of the lumen, with occasional connector struts joining adjacent strings to create a closed circumference unit cell between two such connector struts and two adjacent connected strings there being a plurality of such unit cells arranged in sequence around the circumference between said two adjacent strings; and characterized in that there is a non-constant increment of strut length, serving to displace along the longitudinal axis each unit cell relative to the circumferentially next adjacent unit cell.