When you need to get your flies down fast, the Scientific Anglers Sonar Sink 25 Cold Fly Line delivers unmatched performance and control. Designed with a 25-foot fast-sinking head and a large-diameter handling section, this line achieves quick depth penetration while maintaining excellent line control for accurate retrieves. Built for coldwater conditions, the Sink 25 excels when chasing trout, bass, steelhead, or pike in rivers, lakes, and coastal zones where getting deep quickly makes the difference between a follow and a strike.
Available in two distinct sink rates, the Sink 3 (3–4 IPS) is ideal for shallower lakes, rivers, and moderate currents where a steady sink rate and easy handling are key. The Sink 6 (6–8 IPS) version gets down fast for deeper lakes, reservoirs, and strong currents—perfect for large streamers, heavy flies, and deep drifts. The floating running line and low-tangle design increase casting distance and shooting efficiency, while the braided multifilament core ensures supple performance in cold water without memory or coil.
Enhanced with AST Plus slickness technology, the Sonar Sink 25 casts farther, stays cleaner, and lasts longer than standard sinking lines. Welded loops allow for quick, reliable leader changes, and the SA•ID line identification system keeps your setup organized. Powered by Sonar sinking technology, this line provides smooth, even sink rates and direct fly-to-hand connection—so you can stay in touch with your fly no matter how deep you go.
| S/A SONAR SINK 25 COLD FLY LINE | |||
| Line Weight | Head Length | Total Length | Grain Weight* |
| 150gr (5-6wt) | 25.0' | 105.0' | 150gr |
| 200gr (6-7wt) | 25.0' | 105.0' | 200gr |
| 250gr (7-8wt) | 25.0' | 105.0' | 250gr |
| 300gr (8-9wt) | 25.0' | 105.0' | 300gr |
| 350gr (9-10wt) | 25.0' | 105.0' | 350gr |
*Grain weight for first 25' of fly line
AST + - A new formulation of Scientific Anglers' patented dry-slick technology provides continual line slickness over the lifetime of the line. Up to 50% slicker than the original AST and 200% more durable than the competition. Fly lines with AST Plus cast farther, float higher, and stay cleaner than any other lines ever built.
Welded Loops - Exceptionally slick and strong, Scientific Anglers' Welded Loops produce smoother casts and easier turnover with a seamless fly-line-to-loop transition, making for softer landings and cleaner pickups. The sleek design also maintains buoyancy for improved fly-line flotation and enables quicker connections between fly line and leaders or fly line and backing.
SA Line ID - Meet the Scientific Anglers Line Identification System. SA•ID is an innovative line-marking system allowing you to identify your lines at a glance. Wonder if a shooting head is 200 grain or a 300? Just look at the SA•ID. The SA•ID can be found on the first 1-2 feet of the tip section of your line.
Sonar - For every one fish eating on top, there are ten feeding beneath it. Scientific Anglers' SONAR sinking technology takes flies to where the fish are: beneath the surface. Using proprietary tungsten formulations and unique tapering, the SONAR sinking technology gets flies down, and keeps them there.
