This imitation of an adult mayfly in the dun stage has all the right proportions and properties. It looks natural, feels natural and fish will eat it. If you want to imitate large sized Brown May Dun’s, this is the color to use. We recommend that you use a J:son Swivel for all your fly fishing, no matter what type of fly you are using. However, it is necessary to use a J:son Swivel whenever you fish a size 1 or 2 J:son fly.