Scientific Anglers Fly Lines and Backing

Who Scientific Anglers is

Wikipedia says Scientific Anglers was founded in 1945 in Midland, Michigan, by Leon Martuch, Clare Harris and Paul Rottiers, and MidCurrent's 2013 article also gives 1945 as the founding year. The same article reports that Orvis, based in Manchester, Vermont, had signed an agreement to buy the Scientific Anglers and Ross Reels businesses from 3M, with Scientific Anglers staying headquartered in Midland. Orvis said it planned to keep running the business independently under the Scientific Anglers name, and it appears as an Orvis subsidiary on Wikipedia. That is the ownership picture I can source. I could not open a source that gives the year 3M first bought the company, so I leave it out.

The brand's own site was not reachable when I last tried it, so the product values below come from the maker pages as recorded in our data, and I mark anything that rests only on the Amazon listing.

What Scientific Anglers sells on Amazon US now

At our last check (October 2026) we track 33 Scientific Anglers products on Amazon US: 17 fly lines and 16 backing listings. We found no Scientific Anglers rods, reels or kits there, so this is a lines and backing page.

In the table above, a small mark under each value tells you the source. "Maker" means Scientific Anglers' own page states it, "listing" means only the Amazon listing does, and "—" means we could not confirm it. About half of the lines show maker-sourced values. The rest, and the backing listings that carry only a title, rest on the Amazon listing.

How to read a Scientific Anglers line name

A name like Amplitude Smooth MPX WF-7-F has four parts.

• Series. Amplitude, Mastery, Frequency, Sonar, Air Cel and Magnitude are the series names in our data.
• Descriptor. Smooth, Textured, Infinity, MPX, Grand Slam, Anadro/Nymph, Trout GP, Trout Expert. What each descriptor changes is something the data we have does not explain, so look at the maker's page for the line you are considering.
• Taper. WF means weight forward. The thickest part of the line sits near the front, which makes casting at distance easier.
• Weight and density. The number is the line weight, which should match your rod. F is floating, I is intermediate, S is sinking, and F/S is a floating line with a sinking front section.

The maker's data also lists a length (80 to 100 feet), a core (mostly braided multifilament), and for sinking lines a sink rate in inches per second, with the number after "Type" showing the grade. Our fly line weight chart and types of fly line guides cover the basics.

The Amplitude and Mastery lines

These are the lines with the most maker data in our table.

Amplitude Smooth MPX WF-7-F. A floating line, 90 feet, with a braided multifilament core and a 3 to 8 weight range on the maker's page.

Amplitude Textured MPX WF-5-F. The same length and core, 90 feet, from the Textured descriptor.

Amplitude Smooth Anadro/Nymph WF-6-F. A 100-foot floating line, 4 to 9 range. The name suggests nymph and indicator work, but the data we have does not describe the taper, so I will not guess.

Amplitude Smooth Grand Slam WF-9-F. A 100-foot floating line with a Tropi-Core, rated by the maker for tropical water. A Magnitude Smooth Grand Slam in WF-8-F with a 10-foot clear float tip is listed too, but only the Amazon listing describes it.

Mastery Infinity WF-5-F. A 90-foot floating line with a braided multifilament core and a 3 to 8 range.

The Amplitude Smooth Trout GP and Trout Expert lines and the Smooth Infinity and Textured Infinity are listing-only in our data. Their titles name the weight and taper, and the listing describes the core and floating density, so treat those as the listing's words.

Frequency, Air Cel and the older trout lines

Frequency Boost WF-5-F. The maker lists 85 feet, a braided multifilament core and a 3 to 8 weight range.

Air Cel Floating WF-6-F. The maker lists 80 feet and a 4 to 9 range, braided multifilament core.

MPX Taper WF-7-F. Listing-only: a weight-forward floating line with a welded front loop.

Sinking and sink-tip lines

Frequency Sink Tip WF-5-F/S. The maker lists 85 feet, a 5 to 8 range, and a Type III sink rate of 2.5 to 4.0 inches per second. The sink rate is how fast the sinking section drops, so a Type III sinks faster than an intermediate line.

Sonar Titan Sink Tip WF-6-F/S3. A listing-only sink-tip line, with a float/sink 3 rate of 2.5 to 3.5 inches per second.

Sonar Titan Intermediate WF-8-I. A listing-only intermediate line at 1.25 inches per second. An intermediate sinks very slowly, which suits shallow water where a floating line shows the line to the fish.

If you are not sure you need a sinking line, you probably want a floating line first.

Shooting line

The Freshwater Floating Shooting Line is a 100-foot, 30 pound running line in the data, with a braided multifilament core and a diameter of .038 inch. A running line is the thin line behind a shooting head. It is for people who already own a head and know why they want a separate line.

Backing

Backing is the line under the fly line. It fills the spool so the fly line does not coil tightly, and it is your reserve if a fish runs past the end of the fly line.

Dacron. The maker lists 20 and 30 pound test. We track spools of 100, 250, 3,000 and 5,000 yards. A 5,000-yard spool is enough to reach the next county, so check your reel's capacity before you order one.

XTS Gel Spun. Listed at 50 pound test in 500 yards and at 30 pound test in 250 yards. Gel spun is thinner for a given strength, which means more fits on a small spool.

Colored Dacron, Ultra Premium and similar listings. Eight of the backing listings have only a title and no spec values in our data, including colored Dacron spools and a 50 pound test, 350 yard red Ultra Premium backing. Read the listing's title for the strength and length before you order.

Our backing page lists other brands, and the guides on how much backing to put on a fly reel and the backing knot cover the rest.

What the weight range means

Several lines in the table show a single weight in the name and a wider range in the data, for example a WF-5-F with a 3 to 8 range. The name tells you the size you are buying. The range is the span of rod weights the line can be used on, which the maker lists so you know it will still load a rod that is a size off. A line is happiest on the rod it is named for. The range is useful when a rod is between sizes, or when you want to fish a heavier line on a light rod to help it load at short range.

Length matters less than you think, until it doesn't

The lengths in our data run from 80 to 100 feet. For most trout fishing, 80 or 90 feet is plenty, because in my view most river casts are short. The extra length of a 100-foot line matters when you need to shoot line to a distant flat or fish a big reel with a lot of backing. If you are choosing between a 90-foot and a 100-foot line for a river, the length is not the reason to pick one.

Mistakes to avoid

• Buying by series name. Amplitude, Mastery and Frequency are series. Two lines with the same series name can differ in taper, length and weight. Read the code at the end of the title.
• Buying a sinking line first. A sink-tip or intermediate line casts differently from a floating line and is harder to mend. Start with a floating line unless you already know you need to go deep.
• Overfilling the spool. A spool packed with too much backing can leave no room for the fly line. Work out the backing from the reel's capacity, not from the spool size you can buy.
• Mixing up listings. The table marks which values come from the maker. If a value says "listing", confirm it on the maker's page before you rely on it.

Warranty

We could not confirm warranty terms for Scientific Anglers lines from the maker's pages, so we state none. If you need them, ask the company before you buy, and keep the receipt.

Care and how long a line lasts

A fly line is a coated cord, and the coating wears. Dirt, sunscreen and heat shorten its life. Our guides to how long fly line lasts and how to clean a fly line cover the signs of a worn line and a routine that makes one last.

How to choose

• Trout rod, 3 to 6 weight. A floating line with a length of 80 to 90 feet is the common maker spec in our data. Frequency, Mastery and Amplitude are the series to compare.
• Heavier freshwater rod. An Amplitude Smooth MPX in a 7-weight is the maker-listed example.
• Fly down in current. A sink-tip such as the Frequency Sink Tip.
• Warm saltwater. The Grand Slam lines.
• Tight-line nymphing. Our euro nymphing setup guide explains which kind of line you need, and none of these listings is a euro nymph line by name.

For other brands, the fly lines section and the floating line page set Scientific Anglers beside everyone else we track.