Montane Isotope Hoodie review: an ultralight fleece that ticks all the boxes for more technical and fast-paced outdoor pursuits

The Montane Isotope Hoodie is an ultralight, technical fleece that works well as a stand-alone outer or as part of a layering system

Montane Isotope Hoodie
(Image: © Kieran Cunningham)

Advnture Verdict

The Montane Isotope Hoodie is a great option for hikers, climbers, mountaineers, or anyone else looking for a lightweight, highly packable mid layer that’s simple, neat, and not unnecessarily feature-heavy.


  • +


  • +

    Highly breathable

  • +

    Stretchy fabric

  • +

    Enough warmth for cool summer evenings


  • -

    Hood and hem aren’t adjustable

  • -

    Not enough warmth for stand-alone use in the shoulder season (unless you’re moving fast!)

You can trust Advnture Our expert reviewers spend days testing and comparing gear so you know how it will perform out in the real world. Find out more about how we test and compare products.

Montane Isotope Hoodie: first impressions

The Montane Isotope Hoodie is a technical, ultralight hoodie designed for fast-and-light outdoor adventures. It tips the scales at a tiny 383g (men’s size medium) and has an athletic fit that earmarks it as a contender for best fleece jacket for more fast-paced and dynamic activities like trail running, ski-touring, rock climbing or scrambling. The Isotope doesn’t have a DWR coating (What is DWR?) and is unlikely to keep anything stronger than a moderate breeze out, but its STRIA Lite polyester fabric is highly breathable and uses a brushed backer that offers outstanding next-to-skin comfort, and offers more than enough warmth for summer evenings after sundown. Other endearing features in the Montane Isotope Hoodie include plentiful stretch in the fabric, a duo of zippered, mesh-lined pockets, a hood that’s streamlined and snug enough to fit under a helmet, and articulated arms that provide ample freedom of movement.

Montane Isotope Hoodie

The Montane Isotope Hoodie has an athletic, active fit (pictured is a size large; the wearer is 6'2" and 190 lbs) (Image credit: Kieran Cunningham)

RRP: £70/$90
Sizes (men’s): S – XXL
Sizes (women’s): UK8/US XS – UK 16/US XL
Weight (men’s): 383g/13.5 oz
Weight (women’s): 323g/11.4 oz
Colors (men’s): Arbor Green, Narwhal Blue, Charcoal
Colors (women’s): Wakame Green, Narwhal Blue, Saskatoon Berry
Best use: hiking, climbing, ski touring, trail running, summer mountaineering 

Montane Isotope Hoodie at a crag

(Image credit: Kieran Cunningham)

Montane Isotope Hoodie: in the field 

In the 5 or 6 months that I’ve owned the Montane Isotope Hoodie, it’s seen a lot of action. In the winter months, it frequently served as a light insulating layer beneath my waterproof outer shell. When temps picked up, it soon became a bit of a go-to for hikes, crag climbing, pre-work jogs on chilly days, and any outing on which I needed more than a base layer (see our best base layers) but didn’t want the bulk or burly insulation of a heavyweight fleece or down jacket.  

Here’s how it performed:


The Isotope’s a high performer in the comfort stakes. The brushed polyester is super-soft against the skin and the 3% elastane content in the fabric means that it moves with your body whatever you’re doing. It would have been nice if Montane had added a drawcord to make the hood and hem adjustable, but these both have enough elastication to keep them snug and prevent draughts. 


The Isotope is not a fleece that’s designed for cool nights around the campfire, but comes into its own on summer or three-season hikes when you need a little more insulation than a base layer can provide but would be sweating buckets in a beefy, non-technical fleece or mid layer jacket (for these, see our best down jackets). Simply put, it’s as breathable as fleece mid layers come and a great option for high-output activities, whether you’re wearing it as a stand-alone outer or as a mid layer in a three-part layering system (for more on this, see our guide to hiking layers).


If we were to isolate just the one USP (unique selling point) in this hoodie, it would be its suitability for activities that require unhindered freedom of movement. I’ve carried the Isotope on multiple climbing trips as an emergency heat-booster and each time I’ve had to use it, it has felt like a second skin over my base layer. The stretchy fabric, as you might expect, is largely responsible for this, but the “active”, low-profile fit and articulated arms make it an absolute winner when agility and dexterity are as much of a priority as insulation.   


The Isotope uses a sparing design that forgoes bells and whistles in a bid to keep weight and bulk to a minimum. As such, with the exception of a pair of mesh-lined pockets and that helmet-friendly hood, there’s nothing else that merits mentioning. 

man wearing the Montane Isotope Hoodie

(Image credit: Kieran Cunningham)
Kieran Cunningham

Former Advnture editor Kieran is a climber, mountaineer, and author who divides his time between the Italian Alps, the US, and his native Scotland.

He has climbed a handful of 6000ers in the Himalayas, 4000ers in the Alps, 14ers in the US, and loves nothing more than a good long-distance wander in the wilderness. He climbs when he should be writing, writes when he should be sleeping, has fun always.

Kieran is the author of 'Climbing the Walls', an exploration of the mental health benefits of climbing, mountaineering, and the great outdoors.