Mammut Masao Light Jacket Review

© Dan Bailey

The Masao Light is a lightweight shell that's well suited to three-seasons on the hills, year-round low level walking, and weight conscious uses such as lightweight backpacking or travelling. It has all the features I need in a summer shell, though it's not protective or burly enough for winter hillwalking. Though Mammut are clearly positioning it as an Alpine shell, and several of its features support this, I don't imagine it'd last too well if subjected to regular scrambling or climbing. It's just not built heavy enough! Fast-and-light alpine summer snow peaks? Sure. Rock climbing or Scottish mixed? I think not. In a UK context I think it's better viewed primarily as a walking shell. However, it is light and compact enough to carry on your harness just in case, which beefier shells often aren't.

Using the Masao Light as a windproof layer on a cold, windy Dartmoor  © Dan Bailey
Using the Masao Light as a windproof layer on a cold, windy Dartmoor
© Dan Bailey


At just 238g for a women's size L this is very much a lightweight shell, and though it's not quite up there with the ultralight specialists, I can't see myself ever wishing for something lighter - I need things to be robust enough to cope with the rough and tumble of life outdoors. With the Masao Light you still get a decent hood, pockets and pit zips, so not too many compromises have been made in terms of functionality in order to get the weight down.


A men's version of the Masao Light is also available. I've been using the women's in a size L, which is pretty much spot on for me (I'm usually around a 14).

A simple design that's fairly short in the body   © Dan Bailey
A simple design that's fairly short in the body
© Dan Bailey

Pit zips make this a well-vented shell  © Dan Bailey
Pit zips make this a well-vented shell
© Dan Bailey

It easily fits two or three base and mid-layers underneath without feeling constrained, and at the same time manages not to feel like you are wearing a sail when it is just thrown over a long sleeve t-shirt.

The hem on me comes just to my hips, and drops nicely at the back to ensure you don't feel the draft on the inevitably windy days on the hills. It holds its place when reaching up for a hold (or to climb a tree).

The very simple non-adjustable part-elasticated cuffs make sense in a lightweight shell like this. The fit is quite close which means you don't miss an adjusting strap. You can just about squeeze a bulky glove cuff underneath if needed, but as it is more of a mild weather shell this is unlikely.


Combining a polyamide face fabric with a polyurethane membrane (I'm told), the fabric is light and thin, with a nice soft feel. Its hydrostatic head of 20,000mm is roughly comparable to top-end branded waterproof fabrics. But while its 24,300 g/m²/24h of vapour permeability makes it breathable enough for active use, you do get more impressive figures (at least on paper) from some other lightweight shells. A PFC-free DWR helps shrug off the showers, and after several months' use water is still beading nicely.

Running might not be its main thing, but it'll certainly do in cooler conditions  © Dan Bailey
Running might not be its main thing, but it'll certainly do in cooler conditions
© Dan Bailey

Though you probably wouldn't want to use it as your running mainstay, since it lacks running-specific features such as reflective strips and a roll-away hood, the Masao Light does feel light and breathable enough for occasional running use. I've been wearing it quite comfortably for running in cooler, damp weather, though the flappy hood is a bit annoying. And I've yet to get sweaty in it while out walking, so don't be put off by that mid-range vapour permeability figure. I don't know if it would be breathable enough for running in warmer weather though - I'll have to report back in the spring.


Since its lightness and simplicity are the Masao Light's key selling points, don't expect loads of features. You get just two hand pockets, which on a shell this light is probably all the pocket you'd want. These are roomy enough for bulky gloves, hats etc, and have nice super-light water resistant zips. If you're wearing a harness or a rucksack hipbelt, the pockets are placed high enough to remain accessible.

The pockets are not mesh-lined, so you can't use them to get some air flow. Instead there are pit zips, with a medium-gauge water resistant zip. I've found these really effective when I need extra venting. The chunkier main jacket zip feels suitably robust, and again it's water resistant. Though there's no second zipper, I can't say that's an issue in this fairly minimalist jacket. You do get a decent inside storm flap for when the zip does inevitably leak (in wind and rain they all do eventually).

Ideal for summer hills and year-round walks at a lower level  © Dan Bailey
Ideal for summer hills and year-round walks at a lower level
© Dan Bailey

The hood has a decent peak  © Dan Bailey
The hood has a decent peak
© Dan Bailey

A tiny stuff sack is provided. This I soon lost, as is my habit, and I can't help thinking that a reversible stow pocket would have been better. Either way, the jacket packs down tiny.

There's a single side adjustment toggle in the waist drawcord - and one is really all you need. This fixed adjuster is satisfyingly un-fiddly to operate, and directs the elastic tail up the inside of the jacket so that you don't have a hanging loop to accidentally snag. Top marks to Mammut on this small but important detail.

The hood is fab, nicely shaped for unrestricted head movement and with a slightly stiffened peak which keeps the rain out of your eyes. An interesting elasticated mesh gusset underneath the peak helps it fit well with or without a helmet. The hood is easily tightened with a simple toggle at the back which pulls the mesh to your forehead (or the helmet) and ensures the hood moves with you so your vision is barely obstructed. It is a more fiddly two handed job to try and release the toggle though.

Masao Light in rainy Devon  © Dan Bailey
Masao Light in rainy Devon
© Dan Bailey


This is a lovely, lightweight jacket for less-rigorous three-season use. While it's neither really a climbing specialist (despite Mammut's implying that it is), nor a running shell, it would do fine for either. But really it's ideal for hillwalking, lightweight backpacking and all-round outdoor use. Less demanding alpine summer days would suit it well too. It doesn't feel like it's built to survive regular contact with rock, but so far it is faring well.

The £249 price tag seems a little steep for a jacket of this nature, since none of them are exactly optimised for abuse; however it does feel like excellent quality as far as lightweight shells go, and with a bit of care it ought to last well.

Mammut say:

Reach for the Masao Light HS Hooded Jacket Women when you hear the call of the mountains. The jacket's waterproof outer material is complemented by waterproof zippers and a helmet-compatible hood to protect you from adverse weather. This hard shell jacket also features pre-shaped sleeves and hems that can be adjusted for an individual fit. The jacket's very small packing volume allows you to carry it in your backpack in a special stow bag. Pockets that you can reach even when wearing a climbing harness add the perfect finishing touch to your alpine experience.

  • Weight: 238g wm's sive L (our weight)
  • Sizes: XS-XL (women) S-XXL (men)
  • Water column: 20,000 mm
  • Vapor permeability: 24,300 g/m²/24h
  • With PFC-free DWR treatment
  • Tailored, adjustable, helmet-compatible hood
  • Reinforced hood peak
  • Underarm zipper for optimum ventilation
  • Waterproof Aquaguard front zipper
  • 2 climbing harness-compatible front pockets with waterproof zippers
  • Pre-shaped sleeves
  • Slightly asymmetric cuffs, elastic on the inside
  • Hem width can be adjusted with drawstring
  • Additional stow bag for low packing volume
  • Main Material - Backing: 100% Polyamide
  • Main Material - Face: 100% Polyamide
  • Main Material - Membrane: 100% Polyurethane

Masao Light prod shot

For more info see

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