Cumulus Quantum 350 sleeping bag

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When it comes to finding the right sleeping bag for bikepacking, there is an almost bewildering range of options on offer.

Whether you are an ultra-minimal soloist who thinks nothing of sleeping outside wrapped in the equivalent of tin foil and for whom pneumonia is but a mere inconvenience, or you are more glamper than camper, there is a product out there for you.

F-f-f-freeeezing? Not any more...
F-f-f-freeeezing? Not any more…

However, whichever bag you opt for will almost certainly involve some form of compromise. The lighter the bag, the smaller the amount of fill material, hence the less warm it will be. If you want hydrophobic [water repellent] down, a waterproof shell and enough insulation to comfortably enjoy a winter bivvy, you’ll have to accept a higher cost and larger pack size. For me, a warm bag that packs down small and doesn’t cost the earth was what I was looking for. Enter the Quantum 350 from Cumulus.

Snug as the proverbial bug

Cumulus, who rebranded as Criterion in 2014, has operated in the UK for a number of years. It has a wealth of experience in designing sleeping bags specifically for the UK market and for those overseas conditions most often encountered by Brits abroad – think trips to the Alps.

Add a view, and you're sorted.
Add a view, and you’re sorted.

The Quantum range of bags is designed for those who like to travel fast and light without having to compromise on warmth. The 350 sits in the middle of the range and is comfort rated down to -6°C. Weighing in on my scales at a mere 729 grams, including the 18 gram stuff sac, and packing down to 17cm by 26cm with the supplied staff sac, the 350 immediately ticks the lightweight and small pack size boxes with ease. By using a compression strap, it would easily be possible to reduce the packed volume by a further third.

Unpacking the bag and giving it a good shake, the Polish white goose down lofts up impressively. Despite the bag’s lack of weight, no corners have been cut in the selection of fill material. Compared to some of the competition from the likes of Mountain Equipment and Rab, the fill power of 870 is higher than its nearest rivals which enables Cumulus to keep the weight so low for the level of warmth on offer.

Boxed and baffled.
Boxed and baffled.

In terms of construction, no corners appear to have been cut. It features a full length two-way zip and draft baffle, a basic but effective shoulder baffle to keep the cold out, a hood that can be operated from inside the bag with just one hand and a small inside pocket. The bag is simple in design, with what I would consider the essential features of a good sleeping bag.

Eliminating the zip would save some weight but as someone who sleeps warm, the option of being able to vent with a full length zip is a must have for me. Being a YKK zip, I have no worries about the zip lasting but the ultra-light nature of the Pertex Quantum face fabric means that care has to be taken not to snag the zip on it.

Zippy, not bungled.
Zippy, not bungled.

This is the first time I have used anything featuring Pertex Quantum fabric and it has been a bit of an eye opener. The fabric is luxuriously soft – think 200tpi cotton sheets level of softness. When you crawl inside the bag after a cold day out on the bike, you immediately get a psychological lift. That Pertex Quantum is both waterproof (with its inbuilt DWR+ treatment that can withstand multiple washes) and breathable, which makes it an ideal choice for a down bag. While the stitch-through nature of the bags design means that it isn’t waterproof, I’ve had no issues with condensation affecting the bag on damp camps.

Having used the bag several times in both damp and cold conditions, I can vouch for the warmth and comfort of the bag when the thermometer heads south of zero. I’ve not experienced any cold spots and the bag has worked as claimed. Clearly, there is something to be said for it being designed in the UK. The only downsides I can think of are that I would prefer a slightly jazzier colour than the supplied grey and black and that if you are over 6ft 1in, this isn’t the bag for you as it simply won’t fit! I think Cumulus would do well to produce a slightly longer version for the taller customer as it wouldn’t add a lot of weight to what is a seriously lightweight bag.


Over the months, I’ve come to appreciate the qualities of the Quantum 350. If you are in the market for a down bag that is lightweight, packs down small and is warm enough for the vagaries of the British seasons short of full winter conditions, you would be hard pressed to find a bag as good as the Quantum 350. For me, the search for the perfect bikepacking sleeping bag is over.

Review Info

Brand: Criterion (formerly Cumulus)
Product: Quantum 350 sleeping bag
From: Backcountry Biking,
Price: £270.00
Tested: by CJ for eight months

By day, Sanny plies his trade as a Chartered Accountant and Non-Executive Director. By night, however, give him a map and the merest whisper of a trail "that might go" and he'll be off faster than a rat up a drainpipe on some damn fool mission to discover new places to ride. Rarely without his trusty Nikon D5600, he likes nothing better than being in the big mountains, an inappropriately heavy bike on his back, taking pics and soaking up the scenery. He also likes to ride his bike there too although rumours that he is currently working on his next book, "Walks with my bike", are untrue (mostly). Fat biking, gravel riding, bikepacking, road biking, e biking, big mountain adventures - as long as two wheels are involved, you'll find him with a grin on his face as he dives off the side of a mountain, down a narrow lane or into deep undergrowth in search of hidden trails and new adventures. His favourite food is ham and mushroom pizza and he is on a mission to ride all of the Munros, mostly as it allows him to indulge in eating more pizza. He has no five year plan, is a big fan of the writing of Charlie Connelly and reckons that Kermode and Mayo's Film Review Podcast is quite possibly the finest bit of broadcasting around.

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