Apparatus for use with a delivery catheter, the apparatus comprising an endovascular stent-graft (10, 110, 210, 310), which is configured to initially be positioned in the delivery catheter in a radially-compressed state, and to assume a radially-expanded state upon being deployed from the delivery catheter, and which comprises: struts; and a fluid flow guide, which comprises at least one biologically-compatible substantially blood-impervious fabric, and which is fixed to first and second subsets (32, 34) of the struts, wherein the first and the second subsets (32, 34) do not include any common struts, wherein the struts of the first and the second subsets (32, 34) are elastic such that, when the stent-graft (10, 110, 210, 310) assumes the radially-expanded state: the fluid flow guide defines a lumen having a central longitudinal axis, the struts of the first subset are arranged as a plurality of circumferential cells in circumferentially-continuous rings, which cause the fluid flow guide to define a plurality of substantially cylindrical tubular portions, and the struts of the second subset cause the fluid flow guide to define a bulge having a greatest bulge radius from the central longitudinal axis, which greatest bulge radius is at least 5% greater than an average radius of the substantially cylindrical tubular portions proximally and distally adjacent the bulge, characterised in that: the struts of the second subset define tip portions, and the number of the tip portions of the struts of the second subset that define the bulge is at least 50% greater than the average number of circumferential cells in the two circumferentially-continuous rings proximally and distally adjacent the bulge. struts; and a fluid flow guide, which comprises at least one biologically-compatible substantially blood-impervious fabric, and which is fixed to first and second subsets (32, 34) of the struts, wherein the first and the second subsets (32, 34) do not include any common struts, wherein the struts of the first and the second subsets (32, 34) are elastic such that, when the stent-graft (10, 110, 210, 310) assumes the radially-expanded state: the fluid flow guide defines a lumen having a central longitudinal axis, the struts of the first subset are arranged as a plurality of circumferential cells in circumferentially-continuous rings, which cause the fluid flow guide to define a plurality of substantially cylindrical tubular portions, and the struts of the second subset cause the fluid flow guide to define a bulge having a greatest bulge radius from the central longitudinal axis, which greatest bulge radius is at least 5% greater than an average radius of the substantially cylindrical tubular portions proximally and distally adjacent the bulge, characterised in that: the struts of the second subset define tip portions, and the number of the tip portions of the struts of the second subset that define the bulge is at least 50% greater than the average number of circumferential cells in the two circumferentially-continuous rings proximally and distally adjacent the bulge. the fluid flow guide defines a lumen having a central longitudinal axis, the struts of the first subset are arranged as a plurality of circumferential cells in circumferentially-continuous rings, which cause the fluid flow guide to define a plurality of substantially cylindrical tubular portions, and the struts of the second subset cause the fluid flow guide to define a bulge having a greatest bulge radius from the central longitudinal axis, which greatest bulge radius is at least 5% greater than an average radius of the substantially cylindrical tubular portions proximally and distally adjacent the bulge, characterised in that: the struts of the second subset define tip portions, and the number of the tip portions of the struts of the second subset that define the bulge is at least 50% greater than the average number of circumferential cells in the two circumferentially-continuous rings proximally and distally adjacent the bulge. the struts of the second subset define tip portions, and the number of the tip portions of the struts of the second subset that define the bulge is at least 50% greater than the average number of circumferential cells in the two circumferentially-continuous rings proximally and distally adjacent the bulge.