A stopper rod having an elongate trunk with an upstream first end and a downstream second end, a continuous axial bore extending through the trunk from a stopper inlet in the upstream first end to a stopper outlet in the downstream second end, and a flow control device disposed within the bore to create a backpressure upstream thereof. The flow control device includes a body having an inlet, an outlet and a passageway therebetween, a wire positioned substantially axially in the passageway, and a retainer for maintaining the wire in the passageway. In one embodiment, the retainer is constituted by a portion of the wire itself, which is bent or crimped or configured as a loop; kink or spiral which prevents the wire from being dislodged from the passageway.