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  • Writer's picturePaul

Scientific Anglers Amplitude Smooth Infinity Fly Line Review

Updated: Oct 30, 2021


Keeping a fly line slick can be a real hassle, especially for someone who bank fishes as much as I currently do. Besides just the constant casting and interaction with the water, dragging a fly line over shoreline dirt, rocks, and grass doesn't just remove slickness, but also increases the risk of line damage compared to someone who's just wading or fishing off a boat.

The Scientific Anglers Amplitude fly lines look to address these issues. Available in both a textured or smooth finish like we tested, they offer some solid features to increase castability, fishability, and durability. I've spent the most time with the WF5F but have also been using the WF7F and WF9F versions a fair amount.

Tested Line Weights: WF5F, WF7F, WF9F

Colors: Bamboo/Buckskin/Camo tip and Optic Green/Mist Green/Buckskin (tested)

Overall Length: 90 feet each

Tested Head Lengths: 49–53 feet (varies by size)

Tested Head Weight: Varies by size

Cores: Braided Multifilament

Welded Loops: Yes (2)

Price: $99.95 each

The real star feature of these lines is the AST Plus slickness additive. Rather than just a simple topical coating that can quickly wear off, this additive is unique because it's built down to the core of the line and actually migrates to the surface as the line wears. Simply put, this means the line will stay slick far longer than a typical fly line. Scientific Anglers also says the coating offers up to 5 times less drag and up to 8 times more durability—substantial claims! You can see in-depth info on AST Plus right here.

Built on braided multifilament cores, the lines are rated for cold to moderate temperatures. Some other notable features include a handy line I.D. marked directly on the line, two welded loops, and an improved "Dry Tip" that's said to float twice as high as standard lines.

Out of the box, the lines were supremely slick with no defects to be seen.


These lines are aptly named "Infinity" because they are made for versatility.....or, as Scientific Anglers puts it: "there is no end to what you’ll be able to do with it." They're built with "general purpose" tapers that feature elongated head lengths and taper designs that are made for a broad range of flies and species from small to big. Each head is also built a half-size heavier to help load those fast rods of today. For example, our tested WF5F has a weight of 150-grains for the first 30 feet―that's squarely between the "ideal" target weights for WF5F and WF6F lines set forth by AFFTA.

I find these lines to be simply outstanding to fish with. They indeed cast fluidly and all have a really nice balance of both power and finesse. I've been able to present smaller flies with a fair amount of softness, while the WF9F line I tested had enough muscle to drive out big 6-inch bluegill streamers into the lairs of hungry largemouth bass.

Of course a more specialized fly line will be the very best choice for specific duties like finesse dry fly fishing or routinely casting oversized flies, but these make great choices for folks that don't want or need to have a ton of technique-specific lines for all kinds of different applications. I've been shore fishing these lines here and there for about, oh, eight weeks now, and they've remained plenty slick (especially when wet) with no damage to speak of.

The lines also handle nicely and haven't had any crazy memory or tangling issues to speak of. They mend well, cast great at any distance, and load an ultra-fast rod with good efficiency. I fished the smaller WF5F line on a new Sage IGNITER 590-4 that I recently tested, and it was my favorite out of the three total lines I tested on that rod. While casting or fishing, the green/buckskin color combo I chose for each line makes them easy to track without being too in-your-face bright.


Amplitude Smooth Infinity lines are all floating and come in weights 3-9. There's also several varieties available for more specialized applications like saltwater and trout-specific, and as mentioned, textured Amplitude lines are available as well. All of my Amplitude Smooth lines have been simply awesome thus far, and I hope to try some of the other varieties sometime as well. Although the phrase "game changer" is pretty overused and kind of tiresome nowadays, these lines truly are just that!

Support Demystifly by Purchasing Your Amplitude Line at

Trident Fly Fishing


#LineAndGear #ScientificAnglers #FlyLines

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