Inov-8 ROCFLY G 390 hiking boot review: super materials make super boots

Lashings of wonder-material Graphene in the Inov-8 ROCFLY G 390 hiking boots add up to good news for walkers

Inov-8 ROCFLY G 390 boot
(Image credit: Mark Mayne)
T3 Verdict

Comfortable, precise, fast and grippy are all adjectives that can be applied to the Inov-8 ROCFLY G 390 hiking boots. The only real issue is a lack of waterproof membrane, which will put many off – although it does increase breathability at the same time.

Reasons to buy
  • +

    Very grippy

  • +

    Lots of flex without being sloppy

  • +

    Good energy return

  • +

    Double Graphene props

Reasons to avoid
  • -

    No waterproof membrane

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Welcome to T3's Inov-8 ROCFLY G 390 hiking boots review. Inov-8 has an enviable reputation, a serious commitment and pedigree in proper fell running (the ultrarunning, mountainous kind), and also a parallel drive to find new and super-technical materials to bond into its footwear. The company’s Graphene sole unit made a big splash and won several awards (including a T3 Award), and it's back with more of the same in the Inov-8 ROCFLY G 390 boot. 

Not content with repeating that Graphene sole trick, Inov-8 has gone a step further, adding the super-strong wonder material to the foam in the midsole too. So how do the Inov-8 ROCFLY G 390 boots stack up in the real world? Has the maker of many of today's best trail running shoes repeated its trick to create some of the best hiking boots, too? Read on for the full Inov-8 ROCFLY G 390 boot review…

 Inov-8 ROCFLY G 390 boot review: design and build 

The Inov-8 ROCFLY G 390 boot hits the road with the same G-Grip sole as the award-winning Roclite 345 GTX, reinforced with super-strong and hardwearing Graphene. So far, so good. The new bit is a unique Graphene-infused G-FLY foam that ‘supercharges your feet’, according to Inov-8. It achieves this by delivering ‘25% greater energy return’ (presumably than competitors, although this isn’t specified), and arguably most importantly, retaining this for longer, thanks to the strength of Graphene. 

Inov-8 ROCFLY G 390 boot

(Image credit: Mark Mayne)

The other big news is the massive groove running across under the arch of the foot. Dubbed an ‘adaptor-flex’ groove, the aim is to increase agility without compromising stiffness where it’s needed. After all that excitement, there’s a danger that the relatively straightforward upper will be an anti-climax, but the engineered knit and TPU panels look entirely up to the job. Indeed the ankle is relatively high-cut for such a high-performance boot, and well-upholstered. The lacing is as simple as possible up to the top of the tongue gusset - just holes punched through the TPU armour – but finishes with an alloy hook fastening to cinch that ankle tight. 

Inov-8 ROCFLY G 390 boot

(Image credit: Mark Mayne)

Inov-8 ROCFLY G 390 boot review: comfort and performance 

The Inov-8 ROCFLY G 390 sets a blistering pace in both comfort and performance camps. A featherweight 390 grams means there’s very little weight to cart about, and a solid layer of padding swathes the ankle area, bolstered by the tongue. The result is a snug fit with very little heel lift - the latter aided by the minimalist knitted upper and that deep groove in the sole. While there’s plenty of trainer-style flex on offer, there is stiffness too, and quite a nicely progressive amount, offering more protection than you might immediately imagine. In short, it’s a comfortable boot, with plenty of space for your feet to expand into on longer days.  

Inov-8 ROCFLY G 390 boot

(Image credit: Mark Mayne)

The Graphene-infused G-FLY foam does indeed offer lots of energy return and general bounce, just as claimed. Whether it’s massively better than competitor solutions is hard to quantify, especially given varying thicknesses used in different boots/shoes, and also different road/off road applications, but it’s pretty darn good. There's plenty of plushness to the ride, without feeling bloated and imprecise, which can certainly be an issue with some designs. 

As in previous iterations, the G-Grip sole grips almost startlingly well once it’s bedded in a little, especially on potentially slippery hard surfaces. The 4mm lugs deliver a predictable and robust grip on grass and mud too, although this comes as little surprise, given Inov-8’s fell running pedigree.

Inov-8 ROCFLY G 390 boot

(Image credit: Mark Mayne)

The only fly in the ointment is the lack of waterproof membrane, which does mean hitting a deep puddle will equal wet feet. The TPU does provide some protection around the sides of the boot, but not really on top. That said, there’s a breathability benefit in losing the membrane, especially for drier, summertime adventures. 

Inov-8 ROCFLY G 390 boot

(Image credit: Mark Mayne)

 Inov-8 ROCFLY G 390 boot review: verdict 

There are many positives to the Inov-8 ROCFLY G 390 boot. It’s comfortable, provides acres of bouncy energy return, laces sensibly, weighs very little, and grips like the proverbial to a blanket. On the downside, there’s that missing waterproof membrane, a fact that will bother some more than others, and is an important consideration if you’re venturing off the beaten track into boggier terrain. 

It’s not hard to imagine that Inov-8 has a membrane version in the works, which would result in a very capable lightweight hiking boot that'd be very tough to beat. In the meantime, we’ll have to put up with double Graphene innovation and the resulting comfort on the trail, which is no hardship at all.  If you want breathability and comfort wrapped in a light weight package, and where speed is the overall focus, then these will see you right in all but the soggiest terrain. 

Mark Mayne has been covering tech, gadgets and outdoor innovation for longer than he can remember. A keen climber, mountaineer and scuba diver, he is also a dedicated weather enthusiast and flapjack consumption expert.