Nanoarmor: With a name that sounds straight out of the Stark vault of Iron Man tech Shimano’s new Mastiff line features Nanoarmor, a proprietary technology which features nano-level ridges on the line’s surface. These tiny ridges are designed to help provide extra grip so that knots set properly while preventing the knots from both slipping and breaking, and all without sacrificing any resistance to abrasion and stretch.

Mastiff is a 100% fluorocarbon that features Nanoarmor, tiny nano line ridges that bind to give anglers optimal knot and shot strength

I received some of the new line direct from Shimano and when I ran my fingers over even the larger diameter lines could not detect any of these ridges, the line felt both smooth and supple. Nanoarmor differs from many competing fluorocarbon lines which utilize a soft outer shell to increase knot binding strength. While this traditional method works great for improving knot holding it also has the unintended negative result of adding stretch and impacting abrasion resistance throughout the line.

Like other premium likes Mastiff is precisely wound with perfect consistency
 

I asked Shimano if the nano ridges had any impact on casting distance and feel. They explained that the design improves both as the ridges run linear along the line so that there is less surface contact with rod guide inserts, allowing for less friction and both long and smooth casting performance. The concept reminded me of Scientific Angler’s Sharkskin fly line, only at a much smaller nano level.

I was eager to spool up my Stella FK to cast the new line

I spooled up my Shimano Stella FK with 6lb. Mastiff and head straight for the local lake to make a few casts and found the line very competitive with some of my favorite FC lines. The Mastiff cast so smoothly that I wondered how the nano-ridges would come into play as the line looked totally smooth in bright sunlight, so I headed back to the lab to put the line under our scope.

Under magnification the ridges can be seen

Under a few times magnification I could make out the linear ridges running along the line, and under extreme magnification I was surprised to find the surface didn’t look like traditional smooth line at all and more resembled fabric or even wood grain.

When magnified many times the surface of Mastiff reveals the nano ridges

I am finding that knots hold quickly and cleanly and we will be reporting tensile and knot strength data in more detail in a complete review. Thus far I'm liking the overall handling of Mastiff but have only casted the lighter 4 and 6lb. test lines.

Looking at a knot under the scope. The line does hold very tight and it will be interesting to see how it handles both shock and abrasion

Mastiff was designed by Shimano engineers and will be manufactured in Japan. Like other premium JDM lines this FC looks accurately rated so that diameters are thin and correspond to the various line tests.

Mastiff will be available in 3-20lb tests

Mastiff will be available in 3 through 20lb. tests and is classified as a 100% fluorocarbon main line, though it can also serve as FC leader material.

Mastiff will be manufactured in Japan and become available later this summer in the U.S.

The official launch date for Mastiff will be in July at ICAST 2023, and price points will be announced at that time. My understanding after speaking to the team at Shimano is that availability of the line will be later this Summer.

Spooled up and ready for battle. Time to see how Mastiff performs under the pressure of running fish

Our Quick Take: Shimano’s prostaff have been using Mastiff for a few months now and it was a fluorocarbon line that Gussy recently used to win the Bassmaster classic. In terms of handling, Mastiff feels supple and shoots well and we will be testing the tensile and knot strength on the Machine, as well as seeing how the line holds up to the stress of everyday fishing. I’ve just started fishing with Mastiff and thus far like the way that it handles, and will be comparing it all season with Seaguar Tatsu, my current go-to fluorocarbon line. It will take a lot for me to spool up my finesse setups with something other than Tatsu, given my experience and trust in the line, but I’m looking forward to seeing how Mastiff’s Nanoarmor design translates to performance, and feel, on the water. Shimano's tagline with the Mastiff is "Connected Confidence," let's find out just how strong this new contender really is.