a plurality of pairs of radially expandable undulating cylindrical rings that are longitudinally aligned and are connected at a plurality of intersections to form a plurality of hour-glass shaped cells, each ring having a first delivery diameter and a second implanted diameter,

wherein a first ring of the pair comprises two v-shaped undulations with peaks located circumferentially between two intersections, and wherein the v-shaped undulations comprise long bar arms connected at each intersection, a short bar arm connected to each long bar arm, and a linear or curved bar arm connecting the two short bar arms of each v-shaped undulation;

wherein a second ring of the pair comprises two v-shaped undulations with valleys located circumferentially between two intersections, and wherein the v-shaped undulation comprises a long bar arm connected at the intersection, a short bar arm connected to each long bar arm, and a linear or curved bar arm connecting the two short bar arms of each v-shaped undulation;

a plurality of links comprising linear bar arms connecting adjacent rings, wherein at least one link joins an intersection of the plurality of intersections of a pair of one ring with a linear or curved bar arm of an adjacent ring.