Scientific Anglers Sonar 3D Custom Tip Fly LineCombining SA's custom tip series of fly lines and triple density Sonar technology will keep you in the zone longer. Fly anglers are nothing if not inventive. From splicing together lines to weighing coils on a digital scale, finding the perfect sinking line can be a chore. The SONAR 3D Custom Tip sinking fly line makes all of that much, much easier. This cut to fit fly line allows you to slice off as much line as you need to fit everything from a 7