Dry Fly Fishing - Tips and Techniques presented by Ross Reels The most important factor to dry fly fishing success is fly selection. Three factors play the role in determining what fly to use, size, silhouette, and color. SIZE - falls under the old adage of “match the hatch” anglers need to choose flies that mimic the same size of the insects that are actively emerging. Fish become very selective during the hatch and size can be the most dominant factor. SILHOUETTE - refers to the shape of the f