With a tungsten beadhead, the Pheasant Tail nymph becomes even more effective. Tungsten is heavier than brass, so the fly sinks deeper and faster without adding as much cast-impairing lead. This put the flies in front of fish for a longer drift. The Pheasant Tail Nymph remains one of the top mayfly nymph imitations around, and it can be fished in running or still water. Per 12. Sizes: 12, 14, 16. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Fly Assortments.