There are some fabulously lightweight down jackets around but the key point is not so much their overall weight but how much of that weight is down, as that is the material that keeps you warm, so the more of it in a jacket the warmer that jacket will be.
For all us ‘gram counters’ then we want the lightest jacket consistent with the level of warmth we need, happily you can compare the warmth of different jackets simply by comparing how much down they have in them, called their ‘Fill-Weight’. True a jacket needs to have well designed baffles that allow the down to loft freely but let’s assume that at the top end of the market brands like RAB, Montane and many others have the baffling sorted out.
The Infinity G jacket has 240grams of superior 850 Fill Power down and weighs 404grams for a Medium, compare this with the market leading RAB Neutrino Endurance jacket which has 250grams of 800 Fill Power down but weighs 632grams in a Medium and you can start to understand what the Infinity G is all about.
It should even be slightly warmer than a Neutrino Endurance jacket given the higher Fill Power down but the difference in weight is a staggering 228grams, it’s a third lighter. This means that the fabric of the jacket (excluding the down fill) is just 168grams compared with 382grams in the case of the Neutrino Endurance.
Rab’s Zero G jacket is in the same class – deduct the Fill Weight from the total weight of that jacket and you get 160grams – virtually equal to the Inifinity G (the difference is probably bigger baffles in the Infinity G to allow more space for more down to loft properly). So the choice between the Zero G and Inifinity G is about how much down you want in your superlight jacket shell.
To achieve these low weights you would expect there to be some compromises, and there are, which I’ll come to, first though I want to re-iterate what a superb garment the Infinity G is – 240grams of down is more than some sleeping bags have in them so it falls into the category of a ‘big’ down jacket, rather then an ultra-lightweight fleece replacement – if you need this level of insulation but weight is critical then look no further.
The main way RAB have saved weight is to use ultralight fabric in its construction, inevitably this will be less robust than in heavier garments meaning that the Infinity G needs looking after a bit more, it also means that it has a shiny appearance because such lightweight fabrics can’t be made in a matt finish without adding weight – some people don’t like this shiny finish. The fabric is so thin that you can see the down inside the baffles and this sometimes creates dark areas on the jacket surface.
Feature-wise the key factors are still present – two zipped hand-warmer pockets on the front and a drawcord at the hem, there’s an internal baffle behind the main zipper. The wrists and round the hood are simply finished with an elasticated binding though it’s the hood that has the most compromise – the only adjustment is a Velcro tabbed volume adjuster at the back meaning you can’t cinch it round your face.
All this aside it’s a wonderful piece of kit that delivers the highest warmth to weight ratio available, if you can live with the compromises (which I can) and you need the lightest gear then it must be a contender, if not a ‘shoe-in’.
I recently took the opportunity to test Rab’s new Infinity G down Jacket on the UOG’s yearly backpacking trip. Now I must admit, testing a jacket with 220 grams (women’s UK12) of 850 fill power in the lakes at the end of September, where temperatures were only around 7°C at night might seem a bit extreme, but for someone like me who always feels the cold, the warmth of this jacket became a welcome relief when sitting around camp.
As well as keeping me warm, I knew this jacket would take up little space in my rucksack and at only 378g (UK12) it wouldn’t add much weight either. The Infinity G Jacket packs down really small considering its warmth and even comes with its own little stuff sack. In its stuff sack it packs down to around 21x15cm but on this trip I replaced the stuff sack with a compression bag which took it down to around half the size. I found that the jacket re-lofted well after being stuffed, especially compared to some down jackets which can need a lot of plumping to get it back to its original shape.
I’m really impressed with the overall fit of the jacket. I usually find myself between sizes in Rab jackets (between UK10-12) often going for the larger size which then tends to be too long on my short arms. But with this jacket the 12 fitted perfectly. Not too long on the sleeves (cuffs just covering the back of my hands) and with enough space for a light to mid-weight fleece underneath. There’s not many ‘big’ down jackets that don’t make me feel like the Mitchelin Man once on, but this had a flattening fit and was just long enough to cover my backside (bearing in mind I’m about 5ft 4).
The only thing I had an issue with was with the hood. I admit I have small head (usually resulting in wearing kids size hats) so I found the hood far too big on me. The only adjustment on the hood is a Velcro tab at the back. Even when tightened the slightest bit of wind would push the hood off my head. It will be ideal for my next winter climbing trip as my helmet fit’s under it perfectly, keeping it in place, but by itself it can be a bit of a pain. Personally I would prefer a drawcord adjustment at the front, even if that does mean adding a few extra grams to the jacket.
The rest of the jacket features are very useful. I like that it has a 2-way opening front zip as I will be able to wear it over a harness while still being able to belay comfortably. The 2 hand pockets area a good size – not quite wide enough for holding a map but perfect for holding my gloves, hat, snacks etc, with a smaller internal pocket for storing a phone or keys. The drawcord on the hem allowed me to keep the cold air out and was easy to use, even when wearing thick gloves thanks to the little plastic pull tabs.
I won’t go into the fabrics and down used in the jacket as Rab’s description pretty much has this covered, but I am going to say that I’m glad they used a stitch through construction method as it uses less fabric and is lighter than the more complicated box wall construction and of course means it packs down smaller. Everything I wanted out of the jacket.
Overall I really like the Infinity G Jacket (despite the hood) as it has a high warmth to weight ratio, is super compact and has a really nice fit. This will now be my first choice of jacket for all my Autumn/Winter trips.
On a recent work trip to the Lake District I took the RAB Infinity G down jacket and it did not let me down. I’m the type of person who feels the cold on a moderately chilly day, even when indoors. Stick me next to an open lake in the middle of the mountains and I’ll tell you that I’m freezing! That said, I need a warm jacket to keep my spirits high when sitting around a nippy campsite. It’s a challenge to balance the weight/warmth ratio, I need an insulating layer with a lot of down but I don’t want to add lots of weight to my pack. Although the Infinity G has a slightly bulkier look, it packs down really well into the stuff sack provided and didn’t take up too much space in my rucksack, which is ideal for backpacking.
Considering its low weight, the down fill is impressive - a UK 12 contains 220g of 850 fill power down, with the overall weight of the jacket checking in at 378g. To put this into perspective the RAB Infinity 300 sleeping bag has 300g of 850 fill power down and weighs in at 650g. Of course the difference in overall weight comes down to the features and size but when you consider how much down fill is in this jacket in comparison to the sleeping bag you can start to understand how warm it can be.
The nylon inner is soft to touch and has a nice on the skin feel but I had to be careful to make sure the pocket linings were out of the way of the zips when doing them up as they did snag once or twice. With so much down on the inside of the jacket, the shell is made from a superlight 7d Pertex Quantum fabric to keep the weight down.
Elasticised woven cuffs and a hem draw cord close the body off from the elements, leaving no gaps for cold drafts up the arms or the bottom of the jacket. There are also 2 large zip hand-warmer pockets and a baffled chin guard to help keep you well insulated. The hood is on the larger side, making it compatible for use with a helmet. However, if you are not wearing a helmet there is quite a bit of free space around the head. It could have done with a little more than a loop back adjustment for the non-helmet users amongst us just to make it a little snugger around the head.
On the whole, I rate this jacket highly for helping to retain heat in colder climates and for its very light weight and small pack size. It will definitely be my go to for future camping trips.