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Inov 8 TrailFly Ultra G 300 Max Running Shoe Review

Inov 8 TrailFly Ultra G 300 Max Running Shoe Review
29 April 2021

Words & Photos: Alex Staniforth

Inov-8 have gone bold once again with the TrailFly Ultra 300 G Max, boasting three patent-pending technologies in one shoe. It has a lot to live up to following the success of the TerraUltra G270 and has offered a halfway house for those struggling with low-drop or less cushioning.

The TrailFly offers again something different as their most cushioned model yet, and supposedly the first deeply cushioned shoe on the market that is still responsive over uneven terrain and designed to keep you feeling fresher for longer.

My testing coincided with an unusually dry period in the Lake District and recovering from a knee injury, which conveniently confined me to long, steady miles on the hard-pack trails, paths and roads that the TrailFly is designed for. These were a variety of distances from 8 miles to 30 miles to see if the shoes really do keep up over longer outings.

Initial thoughts

As a chronic ankle roller, like many others I’m instantly drawn to the hefty wedge of cushioning, with the 30mm heel stack reminding me of the Hoka models. This will be inevitably controversial amongst the trail and fell running community, but I’m curious whether Inov-8 have really cracked the sweet spot between the comfort of cushioning, the grip they’re known for, and connection with the ground beneath.

Alex Staniforth Trailfly heel wedge


The shoes fit my wide feet and medium arches comfortably straight from the box, without any obvious hotspots that need bedding in. The toe box is spacious enough whilst stiff enough to support my feet over long outings. These are rated 5 on the Inov-8 width scale, their widest – I’m a size 10 and they feel true to size across the board of similar makes.

Foot protection

As I’d hope from a longer-distance shoe, the wide toe box has a double-layered toe guard which is tough enough to stub the occasional rock on loose trails without noticing. The lacing holds the instep well and the heel box gives plenty of padding, holding securely on steeper sections where I’m up on my toes. The laces are nicely slimmer than the G260 and held firm during three-hour runs. They are just about flexible enough for navigating the terrain whilst keeping my foot secure when fatigue kicks in.


Admittedly I didn’t try these in long sections of wet mud or grass, but the GRAPHENE-GRIP rubber gripped well on polished slabs and occasional slimy rocks, giving a vote of confidence where I might be torn between comfort and a more aggressive tread. The 4mm lugs seem to hit a sweet spot for transitioning across a variety of harder terrains without the unforgiving pounding of deeper lugs underfoot. For racing or muddy terrain I would opt for something more aggressive, but these would make a good all-rounder, ideal for something like the Bob Graham Round leg 5.

Alex Staniforth Trailfly review Traction


The 10mm deep ADAPTER-FLEX groove is behind the new concept that allows both max cushioning and responsiveness. Putting any preconceptions aside, I found this to be mostly true. They had enough flex to move quickly and confidently across uneven rocky trails and sections of gnarly tree roots, transitioning back to smooth gravel paths, and enough lateral support for descending flatter hard-pack trails. I’d be anxious taking these on anything too technical but considering the new innovations I could easily be proven wrong and would need to try this out.


These are instantly comfortable and the cushioning gives a pleasant and much softer contact with hard ground than a typical trail shoe. On a lap of Windermere I was happily covering long sections of unforgiving road without eyeing up grass verges, plus transitioning well between hard pack gravel and singletrack and everything else a long run might throw my way. They have used the lightweight racer tongue which is quite minimal and maybe misplaced with the rest of the spec, but feels supportive enough without any pressure on the instep.


At 300g the TrailFly are not particularly lightweight with so much cushioning, but only 30g heavier than the zero drop TerraUltra G 270, and with the G-FLY foam the difference seems more negatable. I don’t find the weight tires my legs more than would be expected after a few hours of sustained effort, although I’d have to try them over a longer run to be fully sure.

Trail Feel

Inov-8 haven’t held back with the graphene either, now infusing it into the brand new G-FLY foam (a first for any running shoe) which apparently offers a 25% greater energy return and helps you feel faster for longer. It’s not clear to say whether it’s coming from the foam or BOOMERANG insole, but the return is noticeable straight away and I’m flying. It feels like a trip back to my faster road running days, and only road shoes have ever held such an effortless stride. The insole and 6mm drop (heel to toe) encourage my cadence without too much conscious effort. Realistically my legs can only feel so fresh in the final few miles of a 30 mile trail run, but they definitely seem to encourage you to keep the pace up, and I find myself attacking short inclines with an extra sense of momentum. Downhill the extra cushioning really comes into it’s own and I feel well supported to just let myself go.


The use of ADAPTOR-FIT technology offers a supportive fit with breathable mesh. My feet felt comfortable whilst running on a couple of particularly warm and humid days. Sadly they lack the waterproof protection of their GTX models so my feet were quickly wet after a few trail puddles, but they dried equally quickly and kept the mud out.

Alex Staniforth Trailfly review breathable materials


You’ll struggle to miss these with some already dubbing them as ‘G270’s on steroids’. There’s not much chance of going undercover with the fluorescent green outers and boastful bold ‘G’ logo, but I feel like the kid with the new bike riding around the block.

The graphics are fairly basic with striped black and hexagonal imprints, but have a pleasing appearance. It’s a shame more colours aren’t currently available.


With only 150 miles logged it’s too early to pass verdict on durability, but they still feel fresh as new after the first few long runs. However, there’s a robust and bulletproof feel that’s hard to measure, as if they’re built for the long run (quite literally). There doesn’t seem to be any new developments in the upper sections, but the moulding appears more robust with a plastic material extending further round, and hopefully they last as long as the foam.

Overall Verdict

Inov-8 have kicked another brilliant shoe into the market with new innovations that live up to the hype. These are a great all-rounder of comfort without compromising on the grip that you’d need for most long-distance running. The cushioning won’t be for everyone, but I love these shoes and fully expect to see them becoming the weapon of choice for some FKT’s and epic long-distance runs this year. They feel so quick I might even have a go myself!

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