Down or Synthetic? A Buyer’s Guide to Rab Jackets

At Taunton Leisure, we get many questions about many different things, usually about outdoor equipment funnily enough! One thing we’re asked about frequently are Rab jackets.

Whether you’re a walker, climber, mountaineer, or just want to stay warm this winter, you’re going to need something that will keep the cold at bay and stop those teeth from chattering! A warm insulated winter jacket is an essential purchase.

We often get asked about synthetic and down insulation; what’s the difference between them? What’s better? As you may expect, the answers to those questions are not simple. It’s not a case of one insulation being better than the other or one jacket ruling them all. Things are rarely ever that simple!

Rab Jacket: Rab Neutrino Plus
Rab Neutrino Plus aka ‘The Daddy’

In this blog we’re going to look at our range of insulated Rab jackets. If you’ve not heard of them before (where have you been?!) you can find out all you need to know about the company by taking a look here.

The aim of this blog is to help you make an informed decision when it comes to choosing your winter jacket. Think of it as a bit of a buyers guide. Don’t know your Pertex Endurance from your Quantum? Don’t know what fill power is? Want to know difference between a Neutrino Endurance and a Neutrino Plus? Read on!

We offer a wide range in winter jackets from a variety of brands, but for this blog we’re going to be focusing on what we have to offer from Rab. This is a great time to pick up something to keep you warm during those icey cold months!

Taunton Leisure offer Rab products for both men and women and you can take a look at the full range of what we have to offer here. Hopefully this guide will help find the right jacket for you.

Rab Jackets: Down and Synthetic insulation explained

Rab Jacket: Rab Ascent Jacket
Women’s Ascent Jacket

There are essentially two types of insulated jacket in our range from Rab; those that have a synthetic PrimaLoft filling (the Photon Belay, Generator and Women’s Photon for example) and those that have a natural down filling (Neutrino Endurance& Plus, Summit, Infinity and Ascent jackets). Of course, this is a slightly simplistic view, there are far more differences between the products than their filling e.g. outer/inner material, weight, pack size, pocket size, number and location. For now though, lets focus on the filling.

‘So what exactly is down?’ 

Down is a layer of insulation found underneath the feathers of Geese, Ducks and other waterfowl. Rab down jackets use Goose or Duck down clusters that are soft, fluffy and unlike feathers, do not have quills. They hold tiny air pockets which allow warm air to be trapped, making it the best lightweight insulation, natural or synthetic. It is warmer, lighter, more breathable and can be compressed and sprung back to it’s original lofted shape more effectively than a synthetic filling. Rab use a generous ratio of down to small feathers in their jackets, often over 95%.

Goose down is considered a slightly higher quality than Duck down because the clusters of down are larger and thus have more insulating capabilites, more opportunity to retain pockets of warm air as well as being more durable and able to withstand repeated compressing. Rab Jackets that use duck down are sometimes filled with a higher quantity in order to compensate for it’s slightly lower insulation capabilities. Simply put, in dry conditions, down is the highest performing insulation for jackets bar none.

Explaining Fill Power

Not all down is the same, however. There is a scale, known as fill power, that ranks the varying levels of quality and performance in down insulation. A single ounce of down is placed into a plexiglass container and a measurement is taken of how many cubic inches it fills. The scale runs from around 450-900 cubic inches per ounce. Higher numbers indicate a higher quality of down. A Rab jacket with higher fill power (such as the Infinity, with a fill power of 850) will give you the warmth of a different jacket with more filling of a lower fill power, for less weight.

Rab Jacket: Rab Infinity Jacket
Infinity jacket 850 EU fill power at just 460g

Just to complicate things further, EU and US fill power ratings are different! US fill power ratings are 100 points higher, due to the fact that the measurement is taken differently, but the insulation capability will be the same. So a Rab jacket with 750 EU fill power and another with 850 US fill power will have equal performance, providing other factors are the same. So you’re aware, Rab use the EU rating system.

‘What are the differences?’

The thermal efficiency of down is reduced significantly when exposed to moisture. Although, due to the water resistant outer Pertex Endurance fabric (more on that later), they can withstand a shower and are water resistant up to 1000HH.

A synthetic filled Rab jacket, however, will insulate effectively when wet and is generally easier to maintain, but is heavier and has a larger pack size. Down jackets perform best in cold, dry winter conditions and are a favourite of mountaineers, alpine climbers, but will keep you warm if you’re out walking the dog on a chilly morning. As long as it’s not too wet!

Rab Jacket: Rab Photon Jacket
The Women’s Photon Jacket uses
PrimaLoft Sport insulation

Rab use PrimaLoft for synthetic insulation. Our range of Rab synthetic filled jackets use either the PrimaLoft One or PrimaLoft Sport synthetic fibre filling. PrimaLoft was developed for the US Army in the 1980’s and PrimaLoft One has the best warmth-to-weight ratio of any synthetic insulation. When dry, it is the equivalent of a 500 to 550 fill power Goose down.

There isn’t a synthetic insulation that is able to compare to the insulating ability of a high fill power down jacket in dry conditions. In wet conditions, however, a PrimaLoft insulation’s thermal properties far exceed that of down as it is able to maintain it’s loft when wet and still trap body heat.

We’ve spoken to customers who’ve not considered PrimaLoft because the jackets can appear thinner compared to their puffy down counterparts. It’s important not confuse warmth with weight or bulk. A Jacket that may have more filling, weigh more and appear to be ‘thicker’, but that doesn’t necessarily mean it is warmer. A PrimaLoft filled jacket such as the Men’s Generator Alpine will appear thinner, but it will still stay incredibly warm! It works because of it’s microfibre structure. You can fit greater numbers of microfibres into the same space within a jacket than you could larger fibres typical of older synthetic insulations. The microfibres allow for more air to be trapped within a smaller space and consequently less volume is needed to trap the same amount of air, allowing the jackets to be thinner but still retain body heat effectively.

Liam from our Bristol store got hold of the Generator jacket for a hands on test out in the elements. You can read what he thought of it here.

In summary, synthetic is man made and down is natural. Synthetics are easier to clean and maintain, still insulate and maintain loft and shape when wet, but are heavier and less durable than down if repeatedly compressed. Down is lighter, more breathable, less bulky and ultimately warmer in dry conditions.

Pertex? What’s Pertex?!

Pertex is a versatile, wind resistant, durable wicking fabric with more breathing ability than waterproof membranes. Rab work very closely with Pertex and their fabrics combine a class leading weight to strength ratio.

Oh and I know you’re thinking it so I’ll tell you now. Wicking is the process of pulling moisture away from the skin out to the exterior of fabric, where it can easily evaporate.

The most common Pertex fabric in our range is Pertex Endurance. The Endurance material is a very thin, durable and versatile ripstop nylon outer material. It’s 100% windproof, highly breathable and water resistant up to 1000HH. While Rab themselves don’t class it as waterproof, Pertex Endurance keeps moisture out over extended periods ensuring that the filling is totally dry and fully efficient. You’ll find this fabric is the outer material to the Neutrino, Generator, Photon Belay and Summitjackets (to name a few).

Rab Jacket: Rab Ascent Jacket
The Summit jacket uses Pertex Endurance and160D reinforced fabric on ‘abrasion zones'(the black bits!)

Inside many of these jackets you’ll find Pertex Quantum as the inner material. Quantum is lightweight and has a silky, comfortable feel as well as sporting a strong strength to weight ratio. You can also find it in use as the outer material on the Men’s and Women’s Neutrino Vest.

To keep the Infinity we spoke about earlier ultralight and incredibly warm, Rab use the Pertext Quantum GL, an even lighter version of the original Pertex Quantum. This 10 denier ripstop nylon isn’t water resistant like the Endurance, but it’s thin, light characteristics allow the insulation to loft without restriction, enabling the jacket to trap more air and keep the user warmer.

The other Pertex fabric you’ll find used in our range of Rab jackets is the Microlight 30D which can be found on the Women’s Microlight Vest and the Womens Photon jacket. This fabric is one of the softest and lightest in the Pertex range and is often used in Rab’s sleeping bags as it’s dense weave prevents heat loss.

Anything Else?

Well, yes actually, but to go over the in’s and out’s of every difference between each jacket would take a long time so we’ll quickly touch on some of the things to look out for.

  • The reversible chest pocket on the Generator Alpine for packing.
  • Stuff sacks on the down jackets to pack away take up next to no space at all!
  • The softness of Pertex Quantum, it’s really quite something!
  • Helmet compatible hoods.
  • Wired peaks on the Photon Belay, the Neutrino and Neutrino Plus, Generator Alpine and Summit jackets.
  • Laminated windproof zips for extra water repellancy.
  • Storm flaps in front or behind the zips to keep water out.
  • An inner pocket for your drinks bottle, utilising your body heat to prevent your drink freezing in the freezing conditions!
  • Elasticated or velcro adjustable cuffs to keep the wind/rain out.
  • Articulated elbows on the Neutrino plus and the reinforced fabric on the abrasion zones on the Photon Belay and Summit jackets
The Neutrino jacket packs down to
around 24x17cm

So there you have it! Now that we’ve explained down insulation, synthetic insulation; and looked at the various different Pertex fabrics that Rab use in their products and touched on a few extra features too you can now consider yourself to be somewhat in the know when it comes to insulated Rab jackets. Congratulations!

Hopefully this will inform you when perusing our range and help all those numbers make a bit more sense.

More importantly, your new found knowledge will enable you to look smug when your smaller, lightweight jacket is far warmer and more cosy than your annoying friend’s big, bulky coat!

We highly recommend popping into our Taunton, Exeter, or Bristol stores and having a chat with a member of staff about these jackets. They’re all very knowledgeable and happy to help. If you don’t want to leave the house but you just have to know something about any of our products then you can ask a question on our website or on our Facebook or Twitter pages. Don’t forget to ‘like’ and ‘follow’ us!

We hope you stay warm this winter, wherever you are!


Taunton Leisure Online.

A few tips to owning an insulated jacket from Paul in our Exeter Store:

  • Don’t leave your down or synthetic jacket packed away compressed for too long. No more than 24 hours maximum. Doing so runs the risk of your jacket losing it’s loft. Down can withstand more frequent compression than synthetic. 
  • When people ask us about washing a down jacket our advice is usually “don’t” – If you really must then we recommend you get it washed professionally. This costs in the region of £30. While that might seem expensive, your jacket will come back to you looking brand new. You will not be able to clean your down jacket and have it come back any better than if you get it done by a professional.
  • If you really must wash it yourself, then we recommend using a specific down wash, such as Nikwax Down Wash. Then, find the biggest tumble dryer you can and dry on a low heat. Add tumble drying balls, a ball of socks, or something similar. It has been stated that you can use tennis balls (yes, you read correctly, tennis balls), but this advisory. If you use tennis balls, make sure they’re in a sock – tumble dryer balls will work best; they will bounce around inside and help to unclump the wet down.   
  • Do NOT wash with detergent, it will ruin the down.

Oh and what’s the difference between a Neutrino Endurance and a Neutrino Plus? The Plus has 50g more down in it. The outer material is triple ripstop; slightly thicker and harder wearing and is cut longer along the torso for better core insulation. It also has an extra inner pocket!

The Plus also uses a ‘box wall’ baffle construction technique for minimum heat loss. Other down jackets in our range use a ‘stitch-through’ construction; the shell and lining are stitched together to create chambers where the down is inserted. ‘Box wall’ baffles are more thermally efficient as  ‘walls’ of extra material are added to store the insulation. On a ‘stitch through’ construction jacket, heat can leak from the area around the seams where down cannot fill the corners.


A big thanks to Paul from our Exeter store for all of his help relating to this article.
Check us out online @
For the latest news, views, and offers check our Facebook and Twitter pages.
To chat to outdoor enthusiasts and experts on our product ranges visit our stores in Taunton, Exeter, or Bristol. They give pretty good customer service too!
Liam from our Bristol store has blogged about the Generator Alpine Rab Jacket. You can take a look here 
For more on fill power, go here.To find out more about down go to the Plumeria Bay, Ski Adventure Guide and this excellent guide from
Rab’s official website is at

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1 Response

  1. Hi 'Anonymous' The relevant information on baffle construction has been added to the article.Thanks for your reply!- LukeTaunton Leisure Online

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