Scientific Anglers Sonar Series fly lines are all designed to fish below the surface.  They were designed by hard-core anglers to cover a complete range of situations and fish flies through the whole water column.  These lines are fully featured having AST Plus for increased slickness and durability, Sonar technology for controlled sink rates, SA-ID, and Welded Loops.  Temperature rated cores and coatings are used to maximize performance in various situations.

Sonar Titan Sink-Tip Video