Rab Alpha Flash Jacket Review

© Tim Hamlet / Hamlet Mountaineering

The Alpha Flash is lightweight, low bulk and highly breathable fleece. It's an ideal garment for mountain trad, chilly days on the sea cliffs, cold weather hillwalking or just as an everyday out and about lightweight jacket. I've had this top on test throughout the summer and into autumn, and it has fared well as both a midlayer and an outer layer, weather depending.

Rab Alpha Flash on Stac Pollaidh
© Victoria de Ga


The low bulk and slim fit of the Alpha Flash makes it ideal for layering beneath a shell or belay jacket, but when things get a bit sweaty it's just as happy functioning as an outer layer. The stretch fabric allows room for movement in all directions while also maintaining a snug fit against you. There's no excess fabric to flap about and get in the way. I've had this thing out on sea cliffs and mountain crags; in all cases I've worn this as my outer garment while climbing, only sticking on a belay jacket when the wind got a bit mental.

The cuff on the Alpha Flux is a narrow band of stretch material. Designed to be low bulk, this simple style of cuff is used on many jackets these days. They have advantages, but on the downside I don't find they provide as much protection from the wind as a velcro tab that you can fasten nice and tight. On the other hand the collar rises a good way up the neck so if the wind really picks up you can get that zipper right to the top and feel quite comfortable.

Martin McKenna wearing Rab Alpha Flash on The Shelterstone
© Hugh Simons

The final pitch of The Steeple and still perfectly warm
© Hugh Simons


Call me sad, but one of the things that excited me about this fleece was that it actually feels fleecey! There might be a bit of nostalgia playing into this, as I used to wear deep pile fleeces as a kid, but on a practical note I don't think you can make a fleece from anything more snuggly than the 120 weight Polartec Alpha Direct fabric that Rab have used here. Comfort is one thing, but being so fluffy it's also a great fleece for insulation, when paired with a windproof outer - you get plenty of warmth for minimal weight. Polartec Alpha Direct is highly compressible, very breathable and air permeable, and fast drying - ideal stuff for a fleece top for active pursuits, in other words. Along the underside of the arms and sides of the body runs a strip of stretch fabric. This aids in mobility, and adds extra breathability to the garment. The net result is that in cooler conditions you can work hard in the Alpha Flash, without feeling too hot and sweaty.


This is a simple top, and that's very much a strong point. The Alpha Flash has a small zipped chest pocket - just enough for your average smart phone or a couple of cereal bars. Along the front side of the hem you get a drawcord to ensure a snug fit and help keep the breeze out. Running along the inside of the main zip is a strip of material to protect against heat loss and discomfort against the zip. And that's it.

The Alpha Flash at Reiff  © Tim Hamlet / Hamlet Mountaineering
The Alpha Flash at Reiff
© Tim Hamlet / Hamlet Mountaineering


This is a great little fleece from Rab, which has rapidly earned itself a place in my go-to kit for long days on mountain crags, or when out walking in cooler weather. Being so breathable and quick drying, it's likely to prove handy as part of a winter layering system too. The stretchy, low density feel of the Alpha Flash makes it comfy and unrestrictive for climbing, and weighing just 255g (size S - our measure) it is lightweight too - a bonus whether you're wearing it or packing it. At first glance the price tag of £100 may seem a bit steep for a top this simple, but I think the build quality and the top notch Polartec Alpha Direct fabric justify the cost.

Rab say:

Inspired by the latest innovations in fabric technology the Alpha Flash radically reinvents the traditional mid-layer.

From long, cold expeditions with limited resources to fast and light mountaineering the Alpha Flash distils everything you need into one mid-layer. Made from the exceptionally breathable Polartec Alpha, the fabric wicks moisture at an incredible rate, keeping you warm and dry even when you're right at your physical limit.

With flexible fleece panels either side, Alpha Flash will never hold you back; moving with you no matter how strenuous the climb. Extremely packable the Alpha Flash boasts an impressive warmth to weight ratio, making it the alpinist's ultimate cold weather mid-layer.

  • Price: £100
  • Weight: 255g (size S - our measure)
  • Sizes: S - XXL (men's sizing only)
  • Fabric: Polartec® Alpha™ Direct 120 insulation
  • Thermic™ brushed back single jersey with Polygiene® STAY FRESH odour control treatment
  • YKK® Vislon front zip, internal zip flap and chin guard
  • YKK® zipped chest pocket
  • Low bulk cuff construction
  • Half hem drawcord
  • Fit: Slim

Fore more info see

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10 Oct, 2017
So we have gone full circle! Fleece kept you warm but let wind pass through. Then Primaloft, etc, filled garments were as warm but better due to wind resistance, layered easy due to slick lining. Less breathable for on the move though. Polartec Alpha, all of the above but more breathable. Take out slick inner lining, lighter, more breathable, still windproof. Voila, take off outer windproofing, leaving insulation, ie fleece!! So it is a new fleece, with the inherit limitations!? Hmmmmn..... Stuart
Not necessarily the same, but I did smile when we were shown an ice axe without - you wait for it - a rubberised handle at a trade show a few years ago. The reasoning for it's removal was, apparently, because 'it reduced weight and made it slicker + easier to plunge'. What's the chances that in three years, maybe less, we'll be shown an identical ice axe *with* a rubberised handle because it "provides extra grip, making it easier to use". Or maybe I'm just getting too cynical :-)
10 Oct, 2017
It is an odd one isn't it? Polartec Alpha was the big new thing in synthetic insulation, as approved by US special forces no less!, just a few years ago. I wasn't very convinced back then that it was that more breathable, but the outer and inner material seemed crucial So they take the inner liner away, and do what Buffalo did 30 years ago, then take the outer shell away and do what Helly Hansen did 40 years ago! Doesn't mean it's not a great light fleece, but is it any thing more than that? And do the US military feel annoyed they were sold a micro fleece wrapped in a windproof as something new and game changing? ;-)

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