A reinforcing ring (10) for a fenestration (32) of a stent graft which can be surface treated such as by passivation and/or electropolishing. The reinforcing ring has several turns of a substantially inextensible resilient wire (12) in a circular two dimensional planar shape and terminal ends (14) at each end of the wire. The terminal ends each comprising a loop (14) and a tail (16). The tail is folded back and extends around the circular shape. Each of the tails of the terminal loops can have an enlarged end. The reinforcing ring can be straightened out for surface treatment such as passivation and/or electropolishing with substantially no part of the circular shape, the loops or tails touching each other.
