Griffith's Gnat is an excellent dry fly for tailwaters all over. Imitating a midge cluster. It can also imitate a midge if small enough. This trout favorite was designed by George Griffith, Trout Unlimited co-founder. Landing trout all year long, it's probably one of the few drys that work during the winter. The best way to use the Griffith's gnat is the tail end of a double dry setup attached to a tractor fly that is easy to see. Because it's pretty hard to see a Griffith's gnat size 18. You can use it by itself if you got really good eyes. Since it is a drive by I like to use light tapered leader and tippet do. 6X to 7X tapered leader and tippet are excellent choices. I go with 7x if it is a sunny day.