Round Lead Wire is used by fly tier's to weight nymphs and streamers, producing a quicker sink rate. The wire is wrapped around the shank, either by hand or on a bobbin, then covered with thread. These are standard thread sized-spools of soft lead, which will fit in a thread bobbin.
Available in 6 sizes: .010″, .015″, .020″, .025″, .030″, .035″