The Big Test: Three season sleeping bags reviewed (2019)

During spring, summer and autumn, the right 3-season sleeping bag can help make camping in the mountains an idyllic experience. Here’s our pick of the six best down and synthetic sleeping bags for 2019.


The runners up

Mammut Kompakt MTI 3-Season (Women) £159 

Tester: Anna Humphries

  • Lower comfort limit -10°C

  • Insulation Ajungilak MTI Pro polyester 

  • Size 205x80cm (Regular and Short available)

  • Men’s equivalent Kompakt MTI 3-Season (Regular, Large and Wide available) 

  • Packed size 21 x 30cmn 

  • Weight 1851g (inc 100g stuffsack)

This well-priced bag is warmer than other 3-season bags, with a temperature rating of -10°C, while others are -4°C, -6°C or -8.5°C. So not surprisingly, it’s also a little heavier and more bulky when in its stuffsack.

Synthetic insulation means it is less compact but does feel warm instantly, which was a welcome benefit over the down bag I tried, which took more time to become cosy.

The hood, shoulder baffle and zip are all well designed, and there are two sizes each for the women and men’s versions. The women’s option has the extra benefit of a fleece-lined foot area and a bigger hood.

So, what’s not to like? For me this bag’s pink colour with a green zip is a real turn-off. It also lacks the stretchy seams of other higher-priced bags, and is heavy, but of course it is warmer too. Oddly the stuffsack colour is a nice red and black, which doesn’t match the bag but at least the pinkness is hidden when the bag is packed inside!


Price, warmth, fleecy foot in women’s option, two sizes each for men and for women


Weight and packed size, no stretch baffles, pink colour for women’s version 


Vaude Santis 800 SYN £250

Tester: Graham Thompson

  • Lower comfort limit -4°C

  • Insulation Pinnero Mantle 100% recycled polyester

  • Size 220x80cm (one size)

  • Women’s equivalent n/a

  • Packed size 22x28cm

  • Weight 1292g (inc 75g stuffsack)

Like many Vaude products it’s the environmental benefits that shine through with this bag, as it’s made with 100% recycled polyester insulation and its water- repellent finish doesn’t use harmful fluorocarbons (PFC).

Stretch fibres are used in the knee area to allow more comfort, and the shoulder width and length are bigger than some. There’s also a unique additional side zipped arm hole, so you can be inside the bag with both arms out (one arm out via normal side zip, the other through the arm hole).

The weight and packed size are good although, of course, a down bag is even lighter. But also note this is rated as -4°C comfort limit, while other bags here are rated as -6°C comfort limit, so this isn’t quite as warm as the others. There are no extra size or women’s options here either, and the price tag is less friendly than this bag’s impressive environmental benefits.


Environmental benefits, zipped arm opening, stretch panels in knee area, reasonable weight and packed size for a synthetic bag


Price is relatively high compared to other synthetic bags, slightly lower temperature rating, no extra size options or women’s option


Thermarest Hyperion 20F/-6C £400-£420 

Tester: Tim Butcher

  • Lower comfort limit -6°C

  • Insulation Nikwax Hydrophobic 900 fill power goose down

  • Size 216x74cm (Long, Small and Regular available)

  • Women’s equivalent n/a

  • Packed size 16x20cm

  • Weight 688g (inc 50g stuffsack)

New for 2019, this bag is exceptionally lightweight and compact when compressed into its stuffsack. It still carries a temperature rating of -6°C and the weight-saving comes from a numbers of areas. Firstly it uses top quality 900 fill down, so you just need less of it to stay warm, and the shell fabric is very thin 10 denier ripstop nylon.

The side zip only extends to the hip, rather than the foot or calf area, and the zip itself is a lighter-weight design that seems to snag a little easier than others, and tends to open on its own if I didn’t secure the press stud at the top of the zip. There is no shoulder baffle either.

Finally you don’t get the stretch baffles of other sleeping bags. It comes with a pair of thin webbing straps that can be wrapped around a Thermarest sleeping mat for ‘optimal efficiency’, but I didn’t find this of much benefit and felt if I turned over too roughly I may have ripped out the straps.


Weight and packed size. Attachment webbing to sleeping mat may be of benefit to some, but I wasn’t convinced as I tend to sleep on my side and move around too much


Price, short side zip, no shoulder baffle, no stretch in bag size, no women’s specific design



The top three

Deuter Exosphere -6° £170 

Tester: Graham Thompson

Is this synthetic insulated bag so good, there’s no need to spend extra on down insulation?

  • Lower comfort limit -6°C

  • Insulation Thermo Proloft synthetic 

  • Size (Length x shoulder width) 205x68cm (Regular and Large available) 

  • Women’s equivalentDeuter Exosphere -6° SL (one size)

  • Packed size 20x23cm

  • Weight 1319g (inc 88g stuffsack)

It’s good

This sleeping bag uses synthetic insulation, so is available at a much lower price than an equivalent down insulated bag. But the weight, packed size and temperature rating are exceptionally impressive, even compared to down-filled bags.

Elasticated construction allows the whole bag to expand in width by 25%. The elastication also holds the insulation closer to the body, resulting in increased efficiency as there are less cold air pockets, so the bag warms up faster and needs less insulation.

In addition the foot and head have been treated to keep moisture at bay, such as when condensation gathers in a tent. You also get a shoulder baffle, a great hood and a side zip with a good anti-snag design.

I found this bag outstandingly comfortable and warm, and perfect for camping without the cost of a down bag. What’s even better is it comes in both regular and large sizes, as well as a women’s option, and as it is stretchy this bag should fit a wider range of people than most bags.

The compression sack has four webbing buckles to crush the contents, making it easy to create a good packed size.


This bag is rated as -6°C comfort, but a similar weight down bag is rated as -8.5°C. And if you have the cash, a top quality -6°C rated down bag is just 866g, so down is going to be lighter if you compare temperature ratings carefully.

If you’re really picky then this bag could be lighter, with a skimpier stuffsack that vacuum- packs the bag more efficiently. Some grams could also be shaved off by using thinner shell materials, while you could strip out the shoulder baffle and dryzones to save cash too.

There is a chance you may not like the stretchy, body-hugging design. I love it, but some people may want the more spacious feel of a wider bag that doesn’t hug you as closely as this. Finally, some other synthetic bags use more recycled content.


An excellent synthetic-insulated bag that would suit the needs of most backpackers and mountain campers. But pay more and you can have a lighter bag, and if you can live with less features you can pay less or reduce weight.

  • Features 4/5

  • Fit 5/5

  • Comfort 5/5

  • In use 4/5

  • Value for money 5/5



Rab Ascent 700 (Women’s) £260 

Tester: Anna Humphries

This mid-priced down bag offers lots of benefits over synthetic, but is it worth the cash?

  • Lower comfort limit -8.5°C

  • Insulation Nikwax Hydrophobic 650 fill power European duck down

  • Size 205x70cm (one size, women’s)n 

  • Men’s equivalent Rab Ascent 700 (Regular and Extra Long available)

  • Packed size 24x18cm

  • Weight 1325g (inc 66g stuffsack)

It’s good

This is relatively well-priced for a down insulated bag. It uses 650 fill power down (rather than 800 fill power down) to reduce costs, but still has a very reasonable packed size and weight. It also gives you a few extra degrees of warmth compared to some bags, which makes it more suitable for women, who on average feel the cold more than men.

This spacious bag had plenty of room for my hips and legs without feeling tight when I turned over. The side zip extends a good way down to the foot for venting, and there’s also a shoulder baffle to trap air inside.

Hydrophobic down (certified by the Responsible Down Standard to safeguard bird welfare) is used to improve the performance a little more, and is treated with Nikwax to resist moisture. I found the bag did take a little longer to warm up than the synthetic option, but once warm I was extremely cosy and comfortable.

The stuffsack is particularly good, as it allowed me to very easily vacuum-pack the bag down to a very small size.


It is heavier than a bag using down insulation with higher fill power, but of course that is why its price is more competitive. This bag is only available in one size for women too, so if you’re a tall woman you may find you need to look at the longer men’s version.

Some bags have stretch linings to make them even more comfortable and efficient, but that isn’t on offer here. As with any down insulated bag, if it does get damp then its performance drops off rapidly compared to a synthetic bag, although at least here we do have Nikwax-treated down, so this is less of an issue. Of course, while the price is good for a down-insulated bag, if you find the performance of a synthetic bag acceptable you can save a lot of cash by choosing synthetic insulation instead of opting for feathers.


Mid-priced down insulated bag that compares well to costlier down bags. It has most of the key features many mountain campers will need, but pay more and you get a lighter bag, while synthetic options save money.

  • Features 4/5

  • Fit 5/5

  • Comfort 5/5

  • In use 4/5

  • Value for money 4/5


Mountain Equipment Firelite £440

Tester: Tim Butcher

A top-quality down insulated bag with all the features you need, but does it justify the outlay?

  • Lower comfort limit -6°C

  • Insulation 800 fill power Russian goose down 

  • Size 215x65cm (Regular and Long available)

  • Women’s equivalent n/a

  • Packed size 21 x 21cm (size Long)

  • Weight 866g (Long, inc 59g stuffsack)

It's Good 

Designed for ultra- light backpacking and high mountain use, this bag certainly meets its brief. At just 866g and a tiny packed size, this was a doddle to pack into my rucksack and it left plenty of space for other camping equipment.

The bag comes in two sizes, and I tested the Long version given my 198cm height. The width is closer fitting than other bags, but this bag features stretch baffles, so it can expand with your body, but also more loft space is created for the insulation when the lining hugs your body, thereby keeping you warmer.

The insulation is a top-quality down, and the shell material is extremely thin and lightweight. You also get an easy-to-adjust hood and the side zip has a good design that didn’t snag easily. A neck baffle helps prevent warm air from escaping if the hood is not fully tightened. Together this all adds up to a very comfortable bag that was slightly tight across the thigh area but otherwise unrestrictive and warm.

Insulation comes from an audited supply chain called the Down Codex, to ensure welfare standards and quality are high.


To make the bag match my height, sections have been added at the foot, which did mean the side zip doesn’t extend as close to the foot as other bags. So you might get overly warm feet. The bag is narrower than others too, and while it isn’t generally restrictive, a little more thigh space would have been beneficial.

Any bag with down insulation needs to be kept dry, as the insulation will not trap warm air very effectively if it gets damp, so more care is needed here to keep the bag dry compared to a synthetic insulation bag.

This is pretty much a no- compromises bag, and the result is a hefty price-tag that may cause you to, ahem, lose sleep. But for regular backpacking when all- round performance is your need then this is an acceptable price when compared to other options.


Top-quality backpacking bag if you want optimum performance and are prepared to stretch your budget. But the price is quite eye-watering, and synthetic bags perform better if damp.

  • Features 5/5

  • Fit 5/5

  • Comfort 5/5

  • In use 5/5

  • Value for money 3/5



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Rab Infinity 300 (2013)

Rab’s heritage with down products can’t be knocked, and the Infinity 300 – while pricy – has this in its favour before it’s even left the starting blocks. On paper it’s joint warmest bag in our test with the Mountain Equipment Xero, pushing its comfort limit to a more useful -2 deg C with an extreme of -18. The shell fabric – in and out – is Pertex Quantum GL, which is silky and windproof (and a bit transparent!), while the fill is 850 power white goose down. Insulation baffles run the length of the sleeping bag, allowing warmth to travel and improving lofting (fluffing) of the down to an impressive degree. This system – developed by InsoTect – features vertical baffles and ‘flow gates’ to hold the down in place, and is also featured in the Marmot Plasma 30. In use, the Rab Infinity 300 is excellent: luxurious-feeling, fluffy and pretty warm, featuring a shoulder baffle to avoid draughts and a double-ended ¾ zip for top ’n’ tail venting. The bag comes with a cotton lofting sack and a basic stuffsack that you can’t compress – the cinch buckle of which broke on first use, annoyingly. This might seem like a minor gripe, but at this price it really should be perfect.


Weight (with stuffsack) 661g (682g)
Size 215x76cm
Packed size 31x16.5cm
Outer fabric Pertex Quantum GL
Inner fabric Pertex Quantum GL
Insulation 850 fill European goose down
Construction InsoTect Flow trapezoidal vertical baffle
Lower comfort limit -2 deg C
Extreme temp rating -18 deg C



The Rab Infinity 300 is a luxurious sleeping bag, which will no doubt be many people’s favourite. Ideal for spring in the hills; minor quality issues and a high price are the only problems.   

Review by Simon Ingram
First published in Trail magazine August 2013



Marmot Plasma 30 (2013)

sleeping bags





The Marmot Plasma 30 has a very hefty price tag, but this is nevertheless an outstanding sleeping bag that pulls off something rare: it actually seems better than Marmot says it is. In comparison to the Rab Infinity 300 – with which it shares a similar InsoTect insulation system and Pertex outer – it manages a higher fill power of goose down, includes little touches like popper closures on the neck baffle and zip ties, yet manages to weigh less than its rival. This is impressive in itself, but the surprises don’t stop there. The Marmot Plasma 30 feels a lot warmer than it suggests; the quoted comfort limit figure is -1 deg C (the Rab’s is -2 deg C) but the Marmot bag feels instantly warmer when used side by side with the Infinity. This could be due to the higher fill power or simply a better fit due to my body shape, but the high loft of the bag and the snugger fit overall means I personally would select this one for a slightly colder night out. Either way, there really isn’t much in it – and while this is arguably the better bag, for this reason that price is a big turn-off.  


Weight (with stuffsack) 644g (665g)
Size 215x76cm
Packed size 35x17cm
Outer fabric Pertex Quantum with DWR
Inner fabric Pertex Quantum
Insulation 900+ fill goose down
Construction InsoTect vertical baffle
Lower comfort limit -1 deg C
Extreme temp rating -14.4 deg C



The Marmot Plasma 30 is an excellent bag – arguably the best here – though not sufficiently so to justify that price tag over near competitors.

Review by Simon Ingram
First published in Trail magazine August 2013

Rab Neutrino Endurance (2012)

The Rab Neutrino Endurance takes inspiration from both adventure racing and mountaineering, which look for performance at minimum weight. The top half of the bag has regular trapezoidal baffles, which loft (fluff up) well; but the back has varying amounts of insulation, from very little under your torso to well-insulated around the foot. The idea is to save weight where your body crushes the down, rendering it ineffective – which is fine if you lie on your back all night, but often I flip onto my side, at which point I can feel the cold. There’s a half-length two-way internally baffled zip with an anti-snag strip and Velcro security tab. The hood is simple but well-shaped, cinches in well and has a small zipped pocket to one side of your chin that sits outside of the adjustable shoulder baffle. The Neutrino uses highly water-resistant outer fabric, which could give it an advantage in many cases – such as nights in small condensation-prone tents. A comfortable bag with room to move, the Rab Neutrino Endurance has hanging loops and comes with a dry bag compression stuffsack and storage bag.

Weight (bag only) 704g
Size (length x shoulder width x foot width) 220x42x76cm
Packed size 15x28cm
Outer fabric Pertex Endurance
Inner fabric Pertex Quantum and Pertex Endurance
Insulation 800 European goose down and Primaloft draught tube
Construction trapezoidal baffles
Comfort temperature rating +5 deg C
Lower comfort limit 0 deg C
Extreme temperature rating -16 deg C



The Rab Neutrino Endurance’s water-resistant shell could be a distinct advantage in our damp climate, but the fabric edges the weight up to 704g for a 0 deg C bag.

Review by Peter Macfarlane
First published in Trail magazine June 2012

Rab Ascent 500 (2012)

The Rab Ascent 500 has been restyled for 2012 and comes with a good stuffsack that allows it to be compressed smartly for easy packing into a rucksack. The bag feels like it can easily cope with its -5 deg C temperature rating. The foot of the bag is particularly spacious for increased comfort, and the side zip ends about 25cm from the end of the foot, so you can vent your calf area while keeping your feet toasty-warm inside the bag. There is a good anti-snag strip inside the zip to ensure it runs freely and it benefits from a wide and well-insulated draught baffle inside the zip. There is a shoulder baffle that is well-filled with insulation and it has an excellent drawcord design that allows it to be smoothly adjusted to trap air inside the bag. The hood is equally well-designed. A nice added extra is a small zipped internal pocket for valuables. The Rab Ascent 500 is a great bag for all-round camping and backpacking.

Outer fabric 30D Pertex Microlight

Inner fabric 30D Pertex Microlight

Insulation 650+ fill power duck down

Compression packed size 22x18cm

Weight 1220g

Lower comfort temp. rating -5 deg C




The Rab Ascent 500 is the best all-round sleeping bag in our buyer’s guide.

Review by Graham Thompson

First published in Trail magazine Spring 2012

Rab Ascent 900 (2012)

Rab has long been one of the most tried and trusted manufacturers of down sleeping bags, and the Ascent 900 is its best value-for-money option. It features a temperature rating of -19 deg C, so it is warmer than all the lower- priced bags here, yet it still only weighs 1700g including the stuffsack. The bag is a little more spacious inside with a slightly squarer shape than other bags, to make it more attractive to first -time users and general winter campers who may find some closer-fitting bags too restrictive. To keep the weight down the 2012 version also uses Pertex Microlight on the outer and inner. The bag has a long side zip with a wide baffle as well as a wide shoulder baffle. The hood is easy to adjust and fits well. This is superb for those on a budget who also want a bag that is very warm, spacious and lightweight.


Outer fabric Pertex Microlight 30D

Inner fabric Pertex Microlight 30D

Insulation 95/5 down, 650 fill power

Compressed packed size 25x22cm

Weight 1700g

Lower comfort temperature rating -19 deg C



The Rab Ascent 900 is the best budget down bag in our review.


Review by Graham Thompson

First published in Trail magazine March 2012


Rab Alpine 400 2010

Established in 1982, Rab sleeping bags quickly dominated the performance end of the sleeping bag market. But other brands rapidly caught them up and arguably superseded their design. But for 2010 Rab is back with a stunning new range of sleeping bags that look set to place the company back at the top.

The new range of Rab Alpine bags take everything the brand has learnt since the Eighties with the addition of modern materials. Firstly there is the down quality, which is 800 fill power goose down. This is combined with Pertex Quantum, the lightest of the range at 32g/m2, plus Pertex Endurance on the outer for better water resistance as this material has a hydrostatic head of 1 metre, making it almost waterproof except for the seams, which are not waterproof. The Rab Alpine 400 uses the trapezoidal construction method, where each baffle is shaped like a box with sides that taper together a little towards the top. This reduces cold spots without adding too much weight. Also the foot is angled so the toes don’t squash the down in this area. There is an anti-snag webbing tape down the full-length zip. A shoulder baffle completes a great design.

On the hill
The Rab Alpine 400  packs down to a reasonable size and weight for backpacking, but it is not the smallest or lightest here. Tugging it from the stuffsack there is a robustness about the feel of the bag. It feels like it has more insulation and loft than some other bags. But what I liked straight away was that the zip that didn’t snag as easily as some others tend to. The zip baffle is also wider than some other bags, which adds weight and cost, but reduces cold spots of course. The bag is very comfortable thanks to that tapered foot in part, but also the body and hood fit well. The drawcords worked well and this bag felt right straight away. Over recent years I have been less than impressed with Rab bags, but at last we see the brand returning to the quality it was known for in the Eighties. A great product.

In the lab
Our test results (11TOG / -12.5 deg C) were warmer than the manufacturer’s ratings, but this allows performance to drop a little over time and still be within the limits for 3-season use. More importantly there was quality insulation throughout the bag and a water-resistant shell, so the Rab Alpine 400  is good on the hill as well as in the lab.

Size 220x80x48cm
Outer fabric Pertex Endurance
Inner fabric Pertex
Fill weight 400g 90/10 goose down
Fill power 800+
Lower comfort temp rating -6 deg C
Trail temp rating -12.5 deg C
Packed size 35x16cm in stuffsack; 26x16cm compressed
Weight 1090g bag; 64g stuffsack
Made in China (shell), filled in UK
Stores across UK 32
Stockist details tel. (01773) 601870;


The Rab Alpine 400 has a water-resistant shell, tapered foot, excellent zip and baffle; easy-to-adjust drawcords. However, there are lighter and more compact bags, but if you can tolerate the weight, then this is ideal for backpacking in a wide variety of British or Alpine conditions. It won the ‘Best in test’ accolade.

Review by Graham Thompson
First published in Trail magazine Spring 2010

Rab Quantum 800 Endurance 2009

Quantum sleeping bags are designed to be the lightest available for today’s weight-conscious adventurers. Rab’s Quantum 800 Endurance is packed with top-quality down that provides a comfort rating of -18 deg C while the Pertex Endurance shell provides lightweight and water-resistant protection for the insulation. The bag is cut slightly narrow to optimise efficiency while minimising weight and bulk.


Compared to the other sleeping bags featured here the Quantum 800 is the lightest, yet it still gets a manufacturer’s temperature rating of -18 deg C. To maintain warmth without cold spots there is a classic box wall construction, and the 800g of down is well distributed around the bag. The trick to the weight difference comes from a number of areas. Firstly the bag uses top-quality down, so you need less of it to stay as warm. The shell fabric is also very thin, and that too saves a little weight. However perhaps the biggest contributor to the weight saving is the keener sizing, for this bag is narrower and slightly shorter than the others featured here. The bag also benefits from a very light stuffsack, which again shaves a few more grams off the overall weight when packing this in a rucksack. However the stuffsack is not the compression type, which means that this bag is not quite so easy to squash down as others.


On the hill
The bag feels very light as soon as it is removed from its stuffsack, while the soft lining feels particularly nice against the skin. I used this in the Lakes in the mixed weather of November and found that it did not feel as warm as other bags with similar temperature ratings. You get a shoulder baffle and a zip baffle, but there is less insulation in these than in other bags. The narrow profile across the shoulders also meant that insulation in this area was a bit more squashed, and I certainly felt a little restricted in this bag. I’m not particular big, being somewhere between medium and large in clothing, but I definitely would prefer a little more elbow room! Down tended to be escaping in a few places through the stitching, which was unique to this bag. Like a lot of the alternatives the material is water-resistant but not waterproof, so I ended up with some damp down on nights out in this bag. Great for smaller people than me if you don’t need the warmest bag. 


Size 215x75x50cm
Fill weight 800g
Fill power 700+ (EU)/850+ (US)
Comfort temperature rating -18 deg C
Packed size 25x22cm compressed
Weight of bag 1336g
Made in shell: Far East, filled in UK
Stores in the UK 40
Stockist details tel. (01773) 601870;

Verdict: The Rab Quantum 800 Endurance is ideal if you don’t need the warmest sleeping bag, and rate weight and packed size as priorities, but it’s smaller than others so better suited to smaller people.

Rab Women’s Quantum 400

The Quantum range is designed to give the best warmth-to-weight ratio, and this 3-season down sleeping bag does not disappoint. The Tundra bag is 139g lighter, but it has a comfort temperature of +2 deg C, which is not much competition for the Rab’s -7 deg C. Best-quality materials ensure the bag feels really soft and cosy, while the light Pertex fabric means a small packed size, making it an ideal choice for trips where weight, warmth and size are issues. Functional features include baffles along the zip and round the neck, all helping to keep out draughts, and being a women’s fit, the chest width is on the narrower side. But the lightweight fabric on this bag gets easily caught in the zip, making those midnight trips to the loo even more of a mission. Similarly the elastic used for the drawcords is lumpy, making it hard to slide through the cord lock – and with a price tag of £250 this should not be the case.


Size: 210x75x32cm
Outer fabric: Pertex Quantum
Inner fabric: Pertex Quantum
Insulation: 400g of 96% white goose down, 750+EU/850+US fill power
Construction: narrow precurved box wall
Packed size: 32x19cm
Weight: 952g
Made in: UK
Stores in the UK: 19

Verdict: If you want maximum warmth for weight, Rab is still way ahead, but the snagging zip and hood drawcords are annoying.

Rab S12

1790g synthetic sleeping bag; compression stuffsack; wide shoulder baffle; wide zip baffle; reasonable size and comfort; hood fits okay. But zip snagged very easily; minimal insulation in shoulder or zip baffles; not as warm as the -12 rating suggests; Trail temp rating -6 deg C.

Verdict: Buy it if you can find one that doesn’t have a zip that snags and you don’t need the warmest bag.