A reinforcement member (10) for a fenestration in a stent graft (30) comprises a composite wire (12) formed from wire strands of at least two types (14, 16, 18). A first type of wire strand comprises a metal alloy with shape memory characteristics and a second type of wire strand comprising a metal with radiopaque characteristics. The first type of wire strand and the second type of wire strand are twisted or braided together to form the composite wire and then formed into the circular ring with at least two turns of the composite wire forming the ring. The reinforcement member can be a circular ring mounted into a fenestration (40) in a wall (32) of a stent graft, or mounted around a stent graft, or it can be a substantially U-shaped edging along the edge of a scalloped fenestration (44).