Rab have used their new Cirrus insulation for the Nimbus Jacket; Cirrus is a 3M Featherless synthetic insulation that provides a high performance alternative to natural down. It was designed to mimic the look and feel of natural down with all the benefits and none of the drawbacks. It retains two times the loft of down when wet, breathes superbly, has no allergens, retains warmth even when wet (more so than Hydrophobic down), compresses easily and dries exceptionally quickly.
Rab have used this amazing new insulation in the Nimbus jacket, so called as it's like having a little cloud of warmth around you, and produced a lightweight synthetic insulated jacket with the equivalent warmth of a 600 fill power down filled jacket. Mini stitch through baffles keep the insulation in place and give the Nimbus a clean and minimalist look. If you are familiar with Rab products this is like a synthetic filled version of their superb Microlight Alpine Jacket. The filling compresses well when packed and is robust and durable. Its resistance to moisture, warmth when wet and speed of drying are extremely high; superior even to Hydrophobic down and previous synthetic insulation.
Pertex's Quantum fabric is used for the shell, this incredibly lightweight fabric keeps the filling under control, is windproof and highly breathable and an air-permeable Hyperlite nylon lining is used to optimise breathability. The combination of insulation and fabrics provide unparalleled levels of breathability making the Nimbus perfect for active use in cold and damp conditions as a mid layer or stand alone jacket.
The fixed hood is fully insulated and will fit over or under a climbing helmet and you get high quality YKK zips throughout. When not required the Nimbus will pack into its own pocket and stash almost unnoticed into your pack making it perfect jacket for all winter mountain activities.
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Pertex Quantum outer fabric
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100% nylon air-permeable lining
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Cirrus powered by 3M Featherless insulation
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Stitch through mini baffles
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Over or under helmet hood with Lycra binding
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YKK VISLON front zip with internal baffle
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2 YKK zipped hand warmer pockets - left pocket doubles as a stuff sack.
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1 YKK zipped internal security pocket
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Elasticated Lycra cuffs
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Hem drawcord
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Regular fit
How Should Your Insulated Jacket Fit?
Insulated jackets are pedantic little things. Too tight and you'll compress the insulation and limit the warmth capabilities of your brand new jacket, too loose and you'll spend hours warming up the dead space inside the jacket. Getting the correct fit isn't just about aesthetics, it will determine how warm you are.
The Incorrect Fit
Too loose: A jacket which is too loose will keep you relatively warm, however it will take far longer to do so and will waste large amounts of your precious energy. An insulated jacket works by trapping the natural heat that your body gives off in the fibres of the insulation; this creates a micro-climate inside your jacket, keeping you warm and toasty. If your jacket is too loose, heat will be able to escape through the hem, the sleeves and the neck of the jacket; it's a little like sticking the heating on in your car with the windows cracked open - it will heat up, just incredibly slowly.
Too tight: A jacket which is too tight is arguably worse than one that is too loose. If your jacket is far too tight, the baffles can compress to a point where the insulation can't loft effectively, limiting the amount of warmth it can trap. Essentially, it won't work!
The Correct Fit
It's a tricky one to explain, but it's somewhere in the middle. You've first got to consider how many layers you'll tend to wear underneath; will you have just a t-shirt then the jacket, or possibly a baselayer, midlayer and then the jacket? When you've figured out your layers and you've popped your insulated jacket over the top, you shouldn't have any dead space inside. The cuffs and hem should be comfortably sealed around your waist and wrists with room to move. You should be able to lift an arm up above your head without the hem of the jacket lifting more than an inch or so, and the sleeves should be long enough that when carrying out the same motion, they aren't mid-way up your forearm. Your shoulders and chest area should have enough room so that your hands can touch behind your back without feeling restricted.
Additional Information
Lastly, consider which activites you'll primarily be carrying out while wearing the jacket. Are you primarily using it as a winter climbing piece, or an everyday/dog walking jacket? You'll find that technical climbing jackets tend to feature a shorter cut, while urban and casual jackets feature a longer cut to offer additional warmth with less mobility.
To see examples of what a badly fitting and correctly fitting jacket looks like, click here.