A stent graft (1) including a tubular wall (3) with at least one fenestration (40) including a peripheral (37) reinforcement around at least part of the fenestration. There can also be a tubular extension (15). The side arm includes a stent (19) and a cover (17) and extends from and is in fluid communication with the fenestration and the stent graft. The stent may be a self expanding stent. The ring and/or tubular extension provides better support and sealing for an extension arm. The fenestration (40) can be circular or if towards the ends of the stent graft may be in the form of a U-shape (50) with an open end.