Rab Cirrus Flex Jacket Review

© Charlie Low

I was excited to review the Cirrus Flex jacket as it's described on Rab's website as being extremely versatile, both for hiking and climbing. When I reviewed the Alpha Direct jacket recently it quickly became my new favourite jacket, so I was keen to see whether the Cirrus Flex would beat it for top spot. Perhaps not... but it does have a lot going for it.


The Cirrus Flex uses one of the current synthetic alternatives to down, a light fill of 3M's Cirrus Featherless insulation. Its compressibility and ability to re-loft do feel quite down-like, and Rab say that in this regard it is equivalent to 600 fill power duck down. It's worth noting that jackets with fill powers of 700-800+ are available if you're prepared to splash out; in terms of loft and warmth-for-weight, Cirrus Featherless still doesn't beat these higher quality down fills. Unlike down, however, it doesn't clump up or migrate around, and its very low water uptake makes it well suited for use in the UK's damp climate. For its reasonably modest weight the fill feels pretty toasty. The total fill weight starts at 65g for a size 8 and then scales by 10g for each increase in size - 75g for a 10, 85g for a 12...etc.

All-in, the Cirrus Flex is on the lightweight side for a baffled insulated jacket - just 320g for a size 12. As such, it's a good weight for layering under other stuff in cold conditions, or a stand-alone outer for less extreme year-round weather.


The Cirrus Flex is available for women (sizes 8-16) and men (S-XXL). Once again, yet another Rab jacket fits me perfectly. The Cirrus Flex is described on Rab's website as 'a lightweight outer or warm midlayer', and the fit is suited to this: it's snug and figure-hugging enough that it fits under a bigger down jacket or shell easily, and keeps you warm when worn over a long sleeve top for belaying. The length in the hem also means it sits well under a harness.

Front view

Back view


The Women's Cirrus Flex is a pretty good all round jacket. It's a great choice for hiking as it's synthetic rather than down, so you don't need to worry about any rain showers that may strike. The 'Thermic' stretch fleece panelling on the sides increases breathability, allowing you to wear the jacket on the move for longer than you might a standard duvet. In contrast to a puffy all-stuffed design, these low-bulk panels also allow for a good range of movement, meaning it's a good choice for a jacket to climb in.

I usually like using thinner insulated jackets like this as a belay jacket too, but unfortunately there is no double zipper on the Cirrus Flex, so it's not the best choice for throwing on and off in between climbs if it's on the cold side, as you can't easily access your belay loop once it's on.


I usually have to roll up baggy sleeves on jackets when climbing, so I've really appreciated the elasticated cuffs that keep the fit at the wrist nice and close (though the cuffs might not fit well over bulky gloves as a result). The two pockets on the jacket are quite deep, and perfect for storing a decent sized phone, snack, or whatever else you may need to hand. My favourite feature of the Cirrus Flex is the fact it packs into its own pocket, meaning you can clip it to your harness when climbing on sea cliffs or multi-pitch routes. It is a shame there is no belay zip, as this paired with the stuff pocket would be the perfect combo for multi-pitch climbing!

The fleece lined chin is also a nice feature, and feels cosy when zipped all the way up. I would have liked it if the jacket had a hood, but I just end up wearing a hat more because of its absence.


As usual, Rab have done a great job with the little details - the small Rab logo on the back of the neck is a nice feature, and the 'serenity' blue colour I've been wearing has contrasting panelling in dark blue to the main lighter blue. The blue shade of the Cirrus Flex doesn't have contrasting zips which is a shame, as this is a really nice feature on my other Rab jackets. The 'steel' grey Cirrus Flex however does have contrasting zips, which definitely add something.

The Cirrus is made of quite a shiny material, 'Hyperlite' ripstop fabric: this seems strong for its light weight, though aesthetically I would prefer if it was matte. I would also prefer if the jacket had a hood, as without it when fully zipped up the jacket gives a bit of an unflattering 'long neck' effect! Because of this, I wouldn't really wear the jacket apart from at the crag, so in that sense it is a bit less 'everyday' than the other Rab jackets I own.


The Cirrus Flex definitely ticks the 'versatile' box: as a lightweight jacket with a damp-weather-friendly synthetic fill, it's great for hillwalking, long walk-ins, hanging out at the crag and general outdoor use. Its stretchy side panels and the fact it packs into its pocket are good climbing-related features, but in this role it's just unfortunate that its lack of a double zipper means it's not the best belay jacket. Aesthetically I'd have preferred a hood, and a less shiny finish on the fabric, but doubtless there are practical reasons for both. As Rab's least expensive insulated jacket, the Cirrus Flex certainly feels like great value for money.

Rab say:

The Cirrus Flex Jacket is lightly filled with Cirrus 3M Featherless insulation, which balances and regulates temperature so you don't overheat while you're moving or get cold when you stop. Designed for movement, the Thermic stretch fleece panelling offers excellent flexibility and improved breathability. The Cirrus Flex is made with durable Hyperlite rip-stop outer and lining fabric, which sheds water and is fast drying. The left pocket doubles as integrated stuff sack so it packs away neatly when you're on the move.

Whether you plan to walk, climb, or scramble to the summit of the Ben, or beyond, the hard working Cirrus Flex Jacket is suitable for long mountain days and year round active use as part of a layering system.

  • Weight: 320g
  • Sizes: 8-16 (women) S-XXL (men)
  • Hyperlite™ rip-stop outer and lining fabric
  • Cirrus™ 3M Featherless insulation
  • Thermic™ stretch fleece with grid face and brushed back panelling
  • Fleece lined chin guard
  • YKK® VISLON® front zip with internal storm flap
  • 2 YKK® zipped hand pockets. Left pocket doubles as integrated stuff sack
  • 2 Interior drop-in pockets
  • Lycra bound elasticated cuffs
  • Hem drawcord
  • Fit: Slim
  • Centre back length (Size L): 74cm

Cirrus Flex prod shot

For more info see

19 Jun, 2018

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