Rio Fly Line Technology | Rio Product Information

Rio Fly Line Technology | Rio Product Information

For more than 20 years, RIO has demonstrated passion, innovation and a pure love for the sport through its development of the industry’s highest performance fly lines. And the great news is, we will continue to research, design and refine our products to ensure they are your preferred line of choice for years to come.


RIO spends thousands of hours on the water researching, designing and refining products.

In 1990, Jim and Kitty Vincent founded RIO in the mountains of Idaho on the idea that exceptional fly fishing products should be built by anglers for anglers. More than twenty years later, we’re still in Idaho and driven by that same ethos.

Most of us here are your basic passionate fly fishing bums, wading all day in cold, clear Idaho trout streams, lighting delicate dries and heaving huge streamers – hooking, landing, turning loose fish after fish… what a grind. We won’t even mention the horror of having to battle tarpon after bonefish after permit in the balmy turquoise tropics, or braving the wrath of angry chrome in BC.

It’s true, RIO’s cast members donate literally thousands and thousands of hours on the water researching, designing and refining our products, so that when the boss or spouse pushes you out the door to go fishing – yet again – at least you’ll have the pleasure of throwing the highest performance fly lines out there.

And even after all these years of selfless devotion to creating the industry’s most comprehensive and technically advanced fly line tapers (designed for just about every finned creature out there) RIO’s passion remains as strong as when we first began this journey.

Some might smirk and say we’re just fanatics, using our selfish needs to create the most sophisticated, strenuously tested products available… but we call it pride… pride in the promise to give you the absolute, hands-down, best of fly fishing excellence on your rod.

Product development like that won’t happen all by itself – that level of commitment is going to require thousands more hours on the water – but somebody’s got to do it, and that somebody is RIO.


Rio Fly Line Technology Glossary


Agent_X_logo.jpgWe’ve all wanted a higher floating line for a long time but, even as remarkable as our fly lines are, they can’t float without a little technological intervention. Traditionally, getting a line to float has required mixing a bunch of tiny glass balls (called microspheres) into the soupy coating compound prior to the curing phase. The higher you want your line to float, the more glass balls you must add. But this creates a problem in that the microspheres can create a rougher, microscopically abrasive coating that has less plastisol which results in a structurally weaker fly line that cracks.

So, after years of experimenting with exotic compounds and plenty of waist-deep R&D, our lab people discovered an element far more buoyant than the rest of the industry. But the right element was just the start. It took an exponential leap in rethinking the manufacturing process to put it all together. AgentX is a result of the combination of a highly buoyant undercoat coupled with a super-smooth outer coating, and it produces the smoothest, most durable, and highest floating fly lines imaginable.


A customer survey performed by RIO showed that the number one complaint for fly lines was that the tip sank. RIO’s chemists deduced that if one coating of AgentX was so buoyant, then two coats must be, well, really buoyant, and the end result is SFT – Super Floatation Technology. Simply put, this is a manufacturing technique that allows us to fuse two layers of buoyant AgentX coating together. This specialized process is applied to the front few feet of the fly line, producing a tip with a specific gravity of around 0.70. Compare that to the standard s. g. of 0.88 on regular fly lines and you get an idea of just how significant this is.


XS Technology

XS_logo.jpgEvery fly fisherman is looking for a slicker line, and for good reason. Slicker line means longer casts, which is something all anglers strive to achieve. XS Technology is the latest development from RIO’s lab coats that focuses on creating an ultra slick line, with dirt-repelling tendencies.

XS (Extreme Slickness) Technology began when RIO’s chemists began reformulating conventional chemical combinations. Although RIO’s formulas were great, our scientists are fly fishers, and by definition they want an even slicker fly line – it’s just part of the deal. So first, they tackled the polyvinyl chloride (PVC) coating and through intense scrutiny down to the polymeric mix level, (say that 10 times fast) they defined some fundamental limitations. Out went the old PVC/silicone formulas and by methodically adding a little more of this, a little less of that, and a pinch of secret sauce, the lab coats cooked up a completely new and improved recipe.

With XS Technology, RIO has developed a fly line that is slicker, more stable, and far less apt to attract dirt, and paired with AgentX Technology, it engineers a line that is less dense, casts further and more accurately, floats higher, lasts longer, and offers more consistent performance cast after cast, strike after strike, fish after fish.


DualTone is a system perfected by RIO that marks the sweet spot of a fly line by providing an obvious color change in the line. The design of every fly line taper, its most likely application and each individual line size is carefully taken into account, and the location of the color change is unique to each fly line.

Every line model and size is tested on a selection of fly rods to find the ideal place where the rod loads, and the color change starts at that point.

With the DualTone system it is easy to see how much line to strip in, where to pick up a cast, how much line can be held in the air when false casting, and when to make the final cast.

Density Compensation

The majority of modern fly lines feature a taper at the front end, which ensures that they cast smoothly and land on the water without too much impact. With sinking lines and sink tips, this taper creates a small problem; as the line gets thinner the amount of coating on it gets less. The coating is what makes a fly line sink, so as the coating is reduced, the sink rate slows down. Usually this means a tapered sinking line sinks in a curve – with the thicker, heavier and denser body section sinking faster than the tip – not good for controlling the depth, and especially not good for detecting atake, or setting the hook. RIO’s Density Compensation adds a more dense material to the thin tip, which ensures the line sinks straight – better for knowing when a fish takes the fly, and far better for setting the hook. All RIO’s premium tapered sinking lines and sink tips are Density Compensated.

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It’s time to nail down your 2024 fly fishing trip with Minturn Anglers.

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Justin Nolan

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