Wednesday, March 24, 2021

Inov-8 TrailFly Ultra G 300 Max Review: Graphene Powered, Max Cushioned, Adaptable!

Article by Sam Winebaum 

Inov8 TrailFly Ultra G 300 Max ($190 / 195 / £170)


The TrailFly Ultra brings Inov-8 into the world of max cushion trail running shoes for the first time with an innovative “graphene powered” entry. 

Long known for trail runners, and in fact was the very first run shoe company I know of started which started in 2003 exclusively as a trail run shoe company. I ran in many of their early models appreciating their agility but often wishing for more cushion.  Over time the British brand stuck to a fairly static formula of firm, snug and relatively low drop shoes branching out into CrossFit, OCR and some road as the industry seemingly moved on to more cushion and friendlier fits, even in trail.   

2020 saw Inov-8 re-emerge with not only more shoes with their Graphene Grip outsoles but with the sensational Terra Ultra G270 (RTR Review)  a light, agile very versatile zero drop shoe with a lively midsole and of course Graphene Grip! It was the RTR team’s consensus trail shoe of the year and my personal favorite as well.

Graphene a component of both the midsole and outsole. Graphene, whose discoverers were awarded the Nobel Prize is the thinnest, lightest, strongest material ever created. Graphene is incorporated into the outsole and now the midsole of the TrailFly.

With the TrailFly, Inov-8 goes to the other end of the trail running spectrum with an ultra focused max cushion new entry packed with 3 new patent pending technologies.

Graphene Grip

The outsole has sticky traction and graphene based characteristics of being “scientifically proven as  50% more elastic, 50% harder wearing, and 50% stronger”. While I have not been on much granite so far this year as snow is just now disappearing,  in last year’s G270 the outsole was outstanding in the White Mountains. I can say that the TrailFly’s grip in mud has been great given the outsole’s combination of moderate 4mm lugs and deep grooves to the midsole


G-Fly is a graphene enhanced EVA/TPU blend midsole foam which is said to have 25% more “energy return” than standard EVA and 10% more than the already fine rebounding POWERFLOW MAX foam in the G 270. 

The foam was extensively tested in the lab and through up 1200km of wear testing in a single pair and a total of 18K kilometers and is said to remain more consistent in its characteristics and energy return during long runs and over time than conventional foams was illustrated by the research above.


The most unusual and most visible of the 3 patent pending technologies, the TrailFly has a 10mm deep V-shaped midfoot groove through the midsole and outsole to allow the shoe (and foot) to “adapt, react, and mold to uneven terrain”. 

The scientific principle underlying the technology is described as follows:”The flex sits under the midfoot to align with the oblique midtarsal joint axis. This joint’s function is to allow the forefoot to turn inwards or outwards without influencing the same motions in the heel. By having a flex groove under it, the joint is free to do its job. This helps the foot – and shoe – adapt, react and mould to uneven terrain or sudden changes in the trail, while the heel can stay straight.”

In addition, the front longitudinal grooves match the bones of the foot to allow the foot to work with undulating terrain while, due to the stack, being incredibly cushioned. 

I can say this technology is clearly felt and is effective as, even with the giant stack, my foot always feels like it is in the mix with a sensation of ground feel and adaptation to terrain and with the heel always stable,  and especially so on downhills, while the front of the foot is engaged on uphills.

Not a patented tech that I know of,  I was also thrilled that the bouncy 6mm Boomerang sockliner is also in the mix as in the G270 with its expanded TPU beds said to provide 40% more energy return than standard insoles. I did wonder if it was really needed with the deeper softer G-Fly midsole though.


  • Copious softer and forgiving cushion with midsole energy return
  • All day, any surface comfort
  • Very well matched midsole and outsole, smooth flowing run feel on all surfaces. 
  • Totally silent even on road
  • Unusual "natural" sense of ground feel and foot engagement even with giant stack
  • Decoupling at mid foot allows stable downhill landings, easy climbing, flat ground flow and great ground feel despite giant stack height.
  • Superb traction on all surfaces tested without getting in the way on hard surfaces.
  • Roomy yet well held upper.
  • Strong hiking, fast packing, thru hiking option due to stability, plentiful cushion, and traction


  • Weight at 11.92 oz / 338g in a US9 is felt
  • Lacks decisive response on firmer surfaces. Outsole or midsole could be firmer to provide more pop.


Sample Weight: men's 11.92 oz /  338g (US9)  /  women's / (US8)

Stack Height (midsole+outsole): 30mm heel / 24mm forefoot (plus approx. 6mm insole)

Available: Pre-Order March 24, Ship April 8.  


First Impressions and Fit

Sam: A big surprise when I first received it with no details beforehand. I was expecting another svelte, low drop, fast shoe from Inov-8, maybe a “slightly” higher stack, higher drop version of the G 270. What I saw was a giant of a shoe in the class of say a Speedgoat or Saucony Xodus 10.

My sample is a US9 which is half a size up from my true to size.  After trying on and running them and while the midfoot and heel hold is fine in thicker winter running socks I would clearly go true to size in a next pair.

The fit is generous through the mid foot and toe box and is a “Grade 5” or widest toe box in the Inov-8 range. The G 270 was also a Grade 5 but here the volume front and mid foot is yet more generous so those who found the G 270 a bit snug, as it should be for its fast agile purposes, but maybe not so much for super broad feet, should be pleased with this more ultra foot swelling fit here 

The fit has remained more than adequately secure for me even for my narrower right foot at a half size up from normal, not always the case. I noted the called out Adapter-Fit system of overlays and unpadded gusseted tongue did in fact allow me to get a secure comfortable fit despite the half size up. 

One of my test adventures was a 3100 foot /1000 meter hike on smooth packed snow, round trip of about 8 miles and while I used traction spikes I had no slip forward in the shoe on the very steep downhill and only adjusted the laces once the whole day.


The upper material is a fairly simple pliable air mesh that is structured by an array of pliable overlays that, along with the unpadded  tongue and its top of upper connected gusset, do a great job wrapping the foot and comfortably so.

In a super nice touch RoadTrailRun was printed on the tongue!

Lace up is easy and secure but you can see how close the sides are on my relatively narrow feet. 

The heel counter area is moderately padded with the heel counter itself not completely rigid with the rising far rear midsole sidewalls providing some of its structure.

The toe bumper is of a quite pliable, thick and I expect durable two layer construction with the single rear layer over the toes in no way squeezing down over the toes.


The G-Fly midsole is a graphene enhanced EVA/TPU blend. The midsole stack height checks in at 25mm /19mm and that is before the 5mm of relatively soft and forgiving outsole and the 6mm clearly cushioning and energy returning Boomerang sockliner. 

So there is a total of about 36mm at the heel and 30mm at the forefoot which puts the stack in the realm of the Speedgoat (somewhat more) and Xodus (somewhat less) The midsole feel is quite soft and very forgiving and clearly tuned for long days on the trail, be it running or hiking. 

There is measured consistent energy return for sure that is not so much highly energetic and snappy as mellow and pleasing without ever feeling mushy.  The foam has a certain tension to its rebound with no sense of squishing out laterally as softer foams can feel or of harshness as firmer foams can deliver.  

The Adapter Flex 10mm deep groove is clearly felt on the run. On uphills it is felt as a long flexing stable front platform with the rear of the foot and heel of the shoe not interfering with transition and push off. 

On downhills the heel is felt as very stable, torsionally rigid and broad, a solid all of a piece landing platform, rapidly followed by the front of foot moving to toe off with the foot an active participant, and with more flex overall upfront torsionally and longitudinally than the heel, rather than just an appendage that is bolted to the platform. On the flats the effect is of a smooth rolling sensation.

Outsole is up next but must  be mentioned here in context of the midsole and its cushion. The relatively soft and elastic Graphene Grip outsole contributes to the cushion effect of the system. 

Overall, I do wish for a touch more response and snap from what is underfoot. I noticed that on the hardest surface I ran on, concrete sidewalks, the shoe got more noticeably more responsive and snappier than on tar or for sure trail surfaces while also never transmitting much of any shock or being overly firm even on concrete and also  while still retaining a notable sense of energy return from the foam itself. Now try running a Speedgoat on concrete...So while it has the utmost in all day cushion and comfort, I think overall things could be a touch more responsive and snappier. 


The outsole is Inov-8’s Graphene Grip which is said to be “scientifically proven to be  50% more elastic, 50% harder wearing, and 50% stronger”. I cannot yet say for the TrailFly yet but the G270 Graphene Grip proved superb on all surfaces and hard wearing so I expect the same here. Especially notable is its elastic properties which seem to mold to rock and other surfaces and stick.

The outsole’s actual design is of note as it combines 4mm lugs with deeper longitudinal central forefoot grooves into the midsole. 

This design not only performed very well on mud but also for sure contributes to the easy smooth flatter ground toe off for such a big stack shoe, the cushion effect and its total silence on hard surfaces such as road. 

I often attribute a shoe’s silence to the relative firmness of the rubber (and here not super firm) and the overall geometry. Stiff shoes with hard rubber are often very noisy and harder to transition on smoother terrain although some “very noisy” trail shoes such as the upcoming Topo MTN Racer 2 with MegaGrip and road shoes such as Nike Tempo Next can transition and toe off very well indeed due to their overall geometry. 

There is no rock protection plate and in my view none is needed. Protection is good without a plate and further a plate might stiffen the shoe. That said “rock protection” plates, well implemented, can also deliver a propulsive effect which I think the TrailFly could benefit more of or alternativey which firming the outsole a bit might also help provide.



Sam: The ride is very forgiving, quite dynamic with the (Adapter Flex groove and foam characteristics the key contributors)  and this despite the weight and relative overall (midsole+ outsole combination) softness. This TrailFly ride is also notably stable. There is a distinct sensation that foot and shoe flow along the ground all of a piece and in concert with the foot itself and with the uneven nature of the trails in the mix instead of being removed from it as big stack trail shoes often feel,  yet all the while with copious protection and cushion.  

I have run and hiked about 30 miles in the TrailFly to date. The tests included that steep snow hike, a trail run on slightly technical rooty rocky terrain on my usual test loop and 2 runs on a mix of roads and more urban trails. 

On all surfaces the ride was smooth and flowing. I pondered how to best describe the ride and as I ran across an artificial track on one of my runs for a few hundred meters it occurred to me that the feel is quite like running any surface in a moderately well padded road shoe on a track or the feeling of running on very hard packed sand, the toes digging in or across a well mowed firm enough lawn. Of course, we are dealing with a ton of cushion stack here but I would say the geometry and overall cushion is more “natural” and engaged with the foot than other big stack trail shoes.

Conclusions and Recommendations

Sam: This innovative new max cushion shoe packed with effective new technologies will delight runners (and hikers) who are in for long, long hauls on any kind of terrain. 

The Adapter-Flex groove and the front longitudinal grooves are clear highlight features with the distinctly felt action of the geometry on uphills, downhills, and flats with a resulting unique ground feel underfoot working in concert with the massively cushioned platform. 

The graphene enhanced G-Fly midsole and its forgiving rebounding ride and expected longevity is another clear highlight as is the Graphene Grip outsole. Yes it is grippy,  but the outsole design also plays well with the midsole for a unique ride with the foot an active and aware participant in forward motion and terrain unevenness. 

The TrailFly suffers a bit in lacking response and snap on firmer terrain likely due to some of the same factors that give it such great and at the same time forgivingly cushioned ground feel everywhere.

At 11.92 oz / 338g in my US 9 and $190 I wish it was a bit less of both for my uses. I also wish for a variant to sit somewhere between the G270 and TrailFly with a similar 6mm dropped G-Fly foam of the TrailFly and more cushion stack than the G270.  

This said it is clearly a model for long ultras and long days on feet and not as much for the shorter and faster trail runs I usually do. I can’t wait to take it hiking in the White Mountains of New Hampshire where the G270 performed so well but was a bit too minimal in cushion and protection, not to speak of being zero drop, for really long days on the rocks. 

Sam’s Score 9.32 /10

Ride: 9.3(30%) Fit: 9.3 (30%) Value: 8.7(10%) Style: 9(5%) Traction:10(15%) Rock Protect:9.2 (10%)

Watch Sam's Video Review of the TrailFly


Index to all RTR reviews: HERE

Inov-8 Terra Ultra G270 (RTR Review)
Of course sharing a Graphene Grip outsole, the two differ in that the G 270 has far less stack at 21mm zero drop vs 30mm plus for the TrailFly. The G270 is almost 3 ounces lighter. They share a similar upper construction with the TrailFly somewhat roomier. The G 270 was the RTR team's and my personal trail shoe of the year for its outstanding balance of light weight, agility, and sufficient cushion for most runs even as a zero drop shoe. The TrailFly clearly but maybe a bit excessively due to weight and soft response  compliments G 270 (given Graphene Grip and a similar if more rebounding and softer midsole feel)  as the longer easier days shoe in the line up. 

Speedgoat 4 (RTR Review)

At 10.8 oz the Speedgoat is about an ounce lighter and has a 39/35 full stack heigh vs 36/30 for TrailFly, so yet more than the TrailFly and too much for me to move along and feel the trail. Its midsole geometry, stiffness and MegaGrip outsole have it focused on technical terrain with its smooth terrain performance and ground feel not up to the level of the TrailFly despite the weight difference. It’s upper may be more secure for highly technical  uses but in standard widths does not have the volume and comfort of the TrailFly’s upfront.

Xodus 10 (RTR Review)

The closest match up. Weighing about the same, the Xodus 10 has a somewhat lower stack height at 30/26. It’s combination of PWRRUN+ TPU midsole, rock plate, and somewhat firmer outsole deliver a springier, more responsive ride on harder surfaces, making it a great and better road to trail shoe than the TrailFly. The TrailFly has a somewhat softer overall feel and more cushion and considerably more “ground and feet in action” feel. Both have excellent uppers with the TrailFly’s toe box volume greater and its overall feel on the foot lighter and airier. 

Topo Athletic MTN Racer 2 (RTR Review)

The lighter MTN Racer 2, coming April 2021,  reproduces some of the smooth flowing all terrain feel of the TrailFly in a somewhat less cushioned yet still forgiving platform. Shod in MegaGrip, it is a noisy shoe on firmer surfaces unlike the TrailFly.  Fit and sizing is similar with the Topo toe box slightly roomier. 

Salomon Sense Ride 3 and 4 (RTR Sense Ride 4 Review)

I have not run the Sense Ride 4 yet but did the 3. Salomon's most cushioned trail runner weighs considerably less at just over 10 ounces in the current version down from about 10.7 oz in v3. It has dense protective ride with less rebound feel than the TrailFly  suitable for long distances and long days. It is less ground conforming in ride with less feel of the trail and has a lower volume upper. 

361 Yushan (RTR Review)

With a 28/36 stack height the Yushan is a similarly max cushion trail shoe. It weighs half an ounce more at 12.3 oz so really up there. It shares a quite soft and energetic forefoot with a stable heel with the TrailFly and has an easier flex closer to the front of the shoe. More traditional in ride it doesn’t quite match up to the ground feel and dynamism of the TrailFly but is $55 less. 

Tester Profile

Sam is the Editor and Founder of Road Trail Run. He is 63 with a 2018 3:40 Boston qualifier. Sam has been running for over 48 years and has a 2:28 marathon PR. These days he runs halves in the just sub 1:40 range training 30-40 miles per week mostly at moderate paces on the roads and trails of New Hampshire and Utah. He is 5’9” tall and weighs about 164 lbs.

The TrailFly releases April 2021. Pre-orders at March 24

Tested samples were provided at no charge for review purposes. No other compensation was received by RTR or the authors for this review from Inov-8 . The opinions herein are entirely the authors'.

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John H. said...

Just from an aesthetic standpoint, that shoe is hideous. I don't understand the designers who think neon green and black would look great as a trail shoe. Must be a British thing.

Ante said...

That flex groove must attract rocks!?

Sam Winebaum said...

Hi Ante,
so far not as it is V shaped with enough flex so none have got caught. However you do not want to plant a root or as I did a thin rubber flexible water bar in there as I think I did surprising me..

Sam Winebaum said...

John H,
You may recall a very similar color for the launch of the G270 followed very quickly by a spectacular blue and yellow. Not sure what come next for G 300 but I am sure they have a plan
Sam, Editor

Anonymous said...

Your statement about Speedgoat 4 in the comparisons is wrong. SG4 has a 32/28mm stack height, not 39/35.

Sam Winebaum said...

Hi Unknown,
I have clarified. I am referring to full stack height of SG4 "At 10.8 oz the Speedgoat is about an ounce lighter and has a 39/35 full stack heigh vs 36/30 for TrailFly." The Boomerang insole in the TrailFly unlike most insoles is a key component of cushioning stack,
Sam, Editor

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70's Teen said...

Hi Sam,

How would you compare these to the NB More Trail in terms of ride, particularly in a road to trail setting?

Sam Winebaum said...

Hi 70’s Teen,
I don’t have my More Trail here but I would say the key difference for door to trail use would be weight as the More Trail at about 10 oz is almost 1.7 oz lighter and the weight is felt for G300 more so on road than trail. Both have a bouncy energetic ride that is quite similar. Get on the trails and for long days and rough terrain the G300 will be clearly superior in upper hold, stability overall and traction.
Sam, Editor