The Green Copper John Fly is a popular and effective pattern has taken the fly fishing world by storm. This fly sinks quickly and can be used as a deep nymph or a dropper. Fish seem unable to resist the combination of color, flash, and realistic shape. it is best fished where mayflies or stoneflies are common and even works in certain lake situations. Most guides and serious anglers never enter the river without several sizes, colors, and variations of this pattern in the fly box.