The Copper John nymph carries a classic mayfly/stonefly profile. A sleek abdomen reflects light, creating the illusion of movement as well as adds weight to the nymph. The tungsten beadhead adding even more weight, due to its extreme density, giving you the insurance that this fly is getting down quickly. Works great in fast and deep water. Per 2. Sizes: 16, 18, 20. Cancer and Reproductive Harm- www.P65Warnings.ca.gov. Type: Flies.