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  • Writer's picturePaul

RIO InTouch Big Nasty 4D Sink Tip Fly Line Review

Updated: Oct 30, 2021


As winter approaches, many anglers will start thinking about and reaching for sinking lines. There's a bazillion choices available, but quality lines that are density compensated are always my first choice. The new InTouch Big Nasty Sink Tip lines from RIO looked like just the type of lines I'd be interested in, with the added benefit of being geared towards throwing larger "big nasty" flies. Since I fly fish for bass more than anything these days, these lines appeared especially ideal for my style of fishing.

Line Configuration: F / I / S3 / S5

Colors: Orange, Light Grey, Dark Grey, Black combo

Overall Length: 100 feet

Head Length: 39 feet

Core: Braided ConnectCore

Welded Loops: Yes (2)

Price: $99.99

Big Nasty sink tip lines measure 100-feet in length and are really unique because they utilize a "front-loaded weight distribution" and blend multiple densities into one single line. Speaking of just that, my 6-weight tester was the fast-sinking version which is designed with F / I / S3 / S5 sections—that's Floating, Intermediate, Sink 3, and Sink 5. As you can see in the first picture below (courtesy of RIO), the combined sinking portion of the line measures about 20-feet which is not the entire length of the head.

RIO designed this line with Extreme Slickness Technology for a smooth finish and low-stretch ConnectCore for more feel and stronger hook setting. Indeed, my test line was extremely smooth out of the box and didn't sport any defects. There's also a welded loop on each end for easy rigging.


This line has been used for chasing bass out in California as well as bass and cichlids in a couple of deeper spots here in Florida. The thing that jumped out at me immediately was how well this line casts. First off, the line shoots really well and is great to just pick up, haul, and pop right back out there again, even with a beefy fly attached. Second, and most impressive, was how incredibly smooth and stable it felt while casting. There's no clunkiness or otherwise awkward feeling when casting the Big Nasty. The casting performance is just really fluid and I felt that it increased both my enjoyment and efficiency on the water.

In addition to allowing for a very smooth casting line, the gradual step down in densities lets this line sink on a very straight path without any belly or sag that's common with lesser lines. Couple the direct path with the low-stretch braided ConnectCore, and controlling the fly and its depth gets a whole lot easier. RIO states this line as being ideal to fish down to 4–8 feet deep, but I fished my flies down to well over 10 feet with it, though the line isn't ideal for extended presentations at these deeper depths.

Since the majority of the line floats, line control is far better than a full-sink line. You can mend the floating portion easily, and any line that you strip in will float at your feet and won't tangle around snags under the water's surface.


I'm a big fan of this line and hope to use it a ton more in the future. It works extremely well for keeping my bass flies down in the water column and is simply a pleasure to cast and fish with. For trout anglers needing to get streamers down in a hurry while fishing moving water, I can see this line being absolutely awesome for that. Hopefully I'll be back in trout country in the near future and can give that a shot myself.

InTouch Big Nasty lines also come in other versions including full floating, a Floating/Hover/Intermediate sink tip, and a Floating/Hover/Intermediate/Sink 3. In addition, RIO sells a Big Nasty Leader and even Big Nasty Tippet to compliment your fly line for the ultimate capability to turn over big flies.

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