SA Mastery MPX Fly Line Review (Hands-on Tried & Tested)

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In this Scientific Anglers (SA) Mastery MPX review, we’ll take a deep dive into everything that works, what doesn’t, and give you an honest, detailed account of why.

I’ve been casting flies for 35 years and guiding professionally for the last 15. I’ve seen companies come and go, I’ve seen changes and fads, but one thing is for sure, I’ve done A LOT of casting with a lot of lines.

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Why Trust My SA Mastery MPX Fly Line Review?

All reviews are self-research-based reviews. There is no internet info gathering here, only honest reports of the gear we use after hours, days, weeks, months, and even years of use.

Not only have I been fortunate to cast and cast a ton of lines, but I’ve witnessed a multitude of anglers cast them as well. As a professional guide, I get a front-row seat to see how others handle this same equipment.

What’s In The Box?

The Scientific Anglers (SA) Mastery MPX comes, as most fly lines do, in your typical fly line box with the line wound around a plastic spool.

This line is a fresh, cold/cool-water-specific line for targeting mostly trout, bass, and panfish. The MPX came from the previous GPX (general presentation) offering from SA with a little more refinement.

This do-it-all, Swiss army knife of a line is meant to cover the widest variety of situations a fly fisher might encounter. Nymph rigs, medium dries, big dries, and streamers/poppers are all easily doable on the SA MPX.

The Box

The first noticeable thing about the box is its silver coloration with red lettering. Not only does this stand out on a fly store shelf but it also denotes that this line is part of the Mastery series of lines.

SA’s Mastery series is a mid-tier series with lots of added technology but not the whole top-of-the-line arsenal available from SA. The Mastery series retails for $80, just under the Amplitude Smooth and Sonar series at $100, and the flagship Amplitude series at $130.

The Line

For this review, I’ve been using the 5 and 6-weight options. There are two colorways available, amber/willow and buckskin/optic green.

SA Mastery MPX Fly Line laying on ground

The amber/willow is my personal choice as I like a line’s color to be a bit more stealthy. I don’t feel the need to use a hi-viz line like the optic green-tipped version for easier tracking in the drift.

The line looks and feels supple at room temperature but the outer coating does seem slightly firmer than similar lines from other companies.

The Spool

Across the board, fly line spools are all quite similar. Scientific Angler’s label is easy to read and comes with a small sticker/label stating the fly line name and weight.

This label is very handy as it can be placed on your reel, spool, reel case, etc. to remind you of which line you’re dealing with. As someone who has a lot of different lines, reels, and different spools for those reels, this sticker can be very useful.

SA’s spools do come apart if you wish to take your line off but keep it wound or prefer to have it off the spool to line your reel.

There is a pinhole in the center, of course, to slide the spool on a spooler machine or to use a pen/pencil at home to allow the spool to spin as you line your reel.

*Tip – when lining your reel at home, after you’ve tied the backing onto the rear fly line loop, toss the spool into a bowl or bucket of water. The spool will spin catch-free and easily as you reel, no pen/pencil is needed!

SA Mastery MPX Fly Line Review Features & Specs

In my review of SA Mastery MPX Fly Line, the main objectives were build quality, weight, texture, configurations, profile, technology, castability/accuracy, presentation, and warranty.

Here’s what I found:

Build Quality

Scientific Anglers has been one of the leading fly line builders in the game for a long time. Their products are industry-leading and their technological advancements are industry-changing.

The Mastery MPX line, on first viewing, looks like a quality line. The colors (as I’ve seen both in person) are very well chosen for their intended purposes…amber/willow for a bit more stealth, and willow/optic green for visibility.

The feel of the line is on par with most SA lines in that it feels soft and supple enough to cast and mend well but has a finish that’s just hard enough to feel like it’s going to float well and protect the line for a long time.


  • 3 wt – 110 grains
  • 4 wt – 130gr
  • 5 wt – 150gr
  • 6 wt – 175gr
  • 7 wt – 200gr
  • 8 wt – 225gr

For this series, SA weights all the lines a “half-size-heavy” meaning a 5-weight line casts more like a “5.5-weight” line. Overweighting the line is advantageous for today’s fast and ultra-fast action rods.


The MPX line is an all-around, general presentation, floating line for cold to temperate freshwater (trout, bass, pike, carp, etc).

MPX Fly Line

All weights are available in both amber/willow and buckskin/optic green (running line color/head color). As stated, the former is great for stealth and the latter for a highly visible option for those who like to be able to track the fly line easily through the drift.


While Scientific Anglers does add texture to some of their lines, the Mastery MPX is a non-textured line.

The line feel is supple and pliable and the coating is slightly more firm than other lines. I do like this in a cold-water line because (on this particular line, at least) it means the line will shoot through the rod’s line guide with less friction.

It also means that fishing in hot summer months or slightly warmer water for bass and panfish, the line won’t feel soft and spongy in the hand. It also acts as a protective finish shedding dirt, algae, and contaminants.


All weights of the SA Mastery MPX fly line are 90 feet in length.

The running/handling line (back end) is around 55 feet long depending on the head length. The full head length (rear taper, rear belly, front belly/front taper) varies in length by line weight.

Head length:

  • 3wt – 32 ft
  • 4wt – 34 ft
  • 5wt – 36 ft
  • 6wt – 38 ft
  • 7wt – 40 ft
  • 8wt – 42ft

Dual-Belly profile

  • This line features 2 distinct belly sections between the front and rear tapers. The front belly (belly 1) is a larger diameter belly. This focuses weight toward the front of the line for increased capability, especially with big flies/fast rods.
  • The front belly features a spade-shaped, “shovelhead” profile. This means the front taper meets belly #1 and belly #1 has a continuously diminishing diameter until it meets belly #2. Belly #2 has one, continuous diameter until it meets the rear taper of the head.


  • Half-size-heavy – Helps load rods and turn over big flies
  • AST Slickness – An SA proprietary line coating for increased slickness. Helps shoot lines through the rod and helps keep contaminants (dirt, algae, debris, etc) at bay.
  • Welded loops – Easily attach backing and leaders with a loop-to-loop connection (or other knot-to-loop connections).
  • Line ID – The line is printed on the tip with the name of the line, weight, and winding direction. This is very handy when dealing with extra reels and spools, or when changing lines often.


When casting the Scientific Anglers Mastery MPX line, the first noticeable thing is how easily the line loads on fast-action and even mid-fast action rods.

I’ve been using three different rod models for casting this line. All are previous model rods but, being only a couple of years old, they still give a very real sense of today’s rods.

5 wt line – Winston Kairos 9′ 5 wt rod – A typical Winston 5 wt rod has more of a “4.5” wt feel. The Kairos may be a touch more stiff so we’ll call it a 4.75 wt feel for this review.

On the Kairos 5wt, SA’s half-size-heavy feature really shines. It feels as though you’ve got a “3/4-wt” overweighted line. Loading is a breeze and placement is not a problem.

Big flies turn over well and so do nymph rigs. I didn’t throw streamers on the 5 wt however. I can say that the accuracy was quite impressive with a dry and an indicator.

The only problem I ran into was casting the 5wt into a stiff breeze. That does have a lot to do with the rod, however. Many “fast” Winstons I would personally label as “mid-fast.” The line seemed to shoot well at first but lost velocity toward the end of the cast in a stiff headwind.

I don’t know the magic formula but I have had better luck with shooting Rio lines on a 5 wt Winston in general. Perhaps it has to do with the longer head and simply using a different SA line with a Rio-similar head would result in better headwind shoot/turnover on this rod.

I’ve also used two different 6wt rods paired with the 6wt Mastery MPX lines. One was also a Winston Kairos and the other a Scott Flex.

The 6wt Winston experience was similar to the 5wt. The 6wt line, of course, does shoot better into a stiff breeze vs the 5wt. This line really shone on the 6wt Scott Flex though!

A fast-action Scott, in my experience, is faster and stiffer than similarly labeled Winstons. The combo of Scott’s stiff backbone and powerful stroke was a phenomenal pairing with the SA Mastery MPX line.

Both the Winston and Scott 6wts with Mastery MPX line were quite accurate, even in blustery conditions. Still, with the bulk of the line weight toward the front of the head, a full aerial line turnover and a delicate drop into the water with a smaller dry fly were achievable.


The spade-shovel shape and long front taper of the MPX line make general accuracy pretty easy to attain. From tossing a wind-resistant indicator or Chubby Chernobyl to dropping a size 20 BWO spinner on a dime, accuracy shouldn’t be a problem with this line.


Scientific Anglers doesn’t post anything about a warranty on their website. I’ve heard both 1-year and 5-year warranties regarding their lines. This would definitely be from defects, not use and abuse.

I do feel that SA doesn’t post outright about the warranty so that they can make a judgment call on a case-by-case basis. The best thing to do is to send a line with a short letter directly back to SA.

I have seen SA replace almost all lines sent back to them aside from some egregious and obvious misuse cases.

SA Mastery MPX Fly Line Review: My Personal Thoughts


  • Highly useable for a multitude of situations. It is one of the better all-around-use lines available.
  • Slightly firm coating is slick, shoots well, and keeps the line clean longer
  • Has a lot of solid tech but won’t break the bank.


  • Can be a little too stiff for cold-weather fishing.
  • The weight in the head can be a little too heavy for small flies/delicate presentations.

The SA Mastery MPX is a solid choice for a new caster looking for a little better line, an intermediate caster looking for a do-it-all fix, and guides who want solid lines that last, cover many situations, but won’t break the bank.

Most of us fish in warmer weather (spring-fall) and the slick coating will be a welcome advantage. For those who brave winter snows, the line may be a bit stiff. It does everything well except delicate dry fly…but that’s not really the MPX’s intention.

FAQs About SA Mastery MPX Fly Line

Here are a few common questions about Scientific Anglers and their Mastery MPX Fly Line:

What is the MPX line?

MPX (Mastery Presentation – X for “everything”) is the next-gen GPX (General Presentation) line… the same idea, with more features. Its front-loaded head works well for a wide variety of situations from medium/big dries to nymph rigs and streamers. It can work with small dries but there are better lines for that.

What does “half-heavy” mean?

This means that, by AFFTA standards, the 5 wt line weighs the equivalent of a “5.5” wt line (in grains/grams). This slight overloading is advantageous for today’s fast and mid/fast action rods.

How long does the SA Mastery MPX line last?

This always depends on a lot of factors. 100-250 uses is a general idea. For some, that’s one season. For others, one line will last years.

Use, abuse, and cleaning will factor in as well. All lines simply age as time passes too…UV damage, atmospheric breakdown…lines aren’t forever purchases.

What color option is best?

Color is always a personal preference. Dull, subtle colors will camouflage better. Bright colors will stand out. If you want to be sneaky, pick the dull color. If you need to easily track your line in the drift, use the bright color.

Some argue a bright line color doesn’t matter. But I have personally seen fish shy away from bright lines.

Long leaders help but, in the end, being able to see your line in the drift (or know where it is and what it’s doing) is more important than not being able to.

Where is Scientific Anglers line made?

Midland, Michigan, USA


As a guide who goes through lines like a toddler through Pull-Ups, the SA MPX is a great choice. It’s long-lasting, has great tech, works for a very wide gamut of situations, and keeps a little more dough in the bank account for the offseason.

Shop The SA Mastery MPX Fly Line

View the SA Mastery MPX Fly Line and compare prices on AMAZON.

This line will keep you in the game with a multitude of flies and methods from foamy dries to indicators/nymphs, from furry floaty stuff to pounding the bank with big streamers.

While it might not be your best delicate, size 22 trico dry fly line, it can still get it done and handle pretty much anything else you can think of.

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Born and raised in Billings, MT, Nic was blessed to be brought up in an outdoor-minded family. Fishing and hunting were a part of his familial culture. Blame it on my Aquarius birth or some divine design but, from as early as he can remember, he had to be near or in the water. Guiding since the early 2000s, Nic has thousands of hours of fly fishing and guiding experience and has helped hundreds of people get into the sport of fly fishing, or better their skills as anglers.

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