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A fly line is built on a core, and this core is the foundation of the line. It provides the strength and other subtleties of performance – primarily stretch and stiffness. Then a “plastic” coating is applied to the core and this is what we see. There is a profile to that coating known as the taper, and a hundred-foot-long fly line can be a complex series of changes in diameter known as the taper. Modern fly lines and their construction are amazing, and there is a wide range of specialist tapers that are designed to do a job.

The plastic coating is where the “tyre meets the road”; it is what we see and it takes a battering from rocks, feet, chemicals, sunlight, and seemingly a hundred other things that can damage it. So, between the core and the coating, a seemingly simple fly line has many subtle features. Some of them are:

  • low stretch cores for bite detection and hook set; plastics and cores that can withstand the fierce heat of the tropics or remain limp enough to use within the Arctic Circle;

  • tapers that are designed to carry ridiculously large flies;

  • tapers that present size 22 flies delicately and from a long way off;

  • lubricants and UV protection; and

  • additives that keep the plastic flexible and durable.

few years ago, RIO set out to rethink its fly lines and recognised the importance of the properties of the core. It spent several years experimenting with various materials and these experiments have paid off with low-stretch lines that are not just brilliant for casting but especially for bite detection. These are at the heart of RIO’s Elite series of lines. Concurrently, Rio also focused on the properties of the coatings that went onto these super new cores.

Putting taper profiles aside, the actual plastic used for the coatings also went under an exhaustive “re-engineering” process, with a focus on slickness and durability utilising the very latest in plastics technology. All lines are quite slick when new but, after a few months of use and abuse, things can change, and here’s where the slickness and durability of RIO’s new coatings really emerge. Slick line shoots through the guides easily so there’s less false casting, and hence less wear. It’s far more efficient, and of course this adds considerably to casting and fishing pleasure. Greater slickness also means less effort, and this means smoother loops and more distance.

The lines that emerged from this five-year project are known as the Slick Cast lines. And they’ve been used and abused around the world by a team of RIO’s field testers. After months of use, these new RIO Slick Cast lines remain slippery like new, and are clearly very tough, with claims of 140% more durability. Further, it is claimed that even in the tropics, an environment that’s relentlessly tough on fly lines, this slick finish has remained excellent after months of fishing.

Left: What isn’t tangible about RIO’s Slick Cast is the durability. You certainly won’t appreciate it on Day 1…you’ll be too busy drooling over your casts. You’ll start to recognize it on Day 25, you’ll appreciate it on Day 50, and you’ll be blown away by it on Day 80.

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