Cumulus Quantum 350 2010

Quantum bags are the lightest in the Cumulus range and they are designed to offer a superb warmth-to-weight ratio. So they use the best down available and combine this with superlight fabrics. To save a little more weight those in the Quantum range are slightly shorter and narrower than other Cumulus sleeping bags.

The Cumulus Quantum 350 is designed to optimise performance for weight, so it makes use of a trapezoidal construction. This is like a box wall construction with sloping sides to each box and it results in a bag that is warmer than box wall as cold spots are reduced between each box of insulation. This is also a lighter construction method than V-shaped boxes. The down is also top-quality, being 870 fill power Polish goose down. These features are combined with Pertex Microlight fabrics that weigh in at only 50g/m2 and Pertex Quantum, which weighs 32g/m2. The bag is also made with a differential cut so the top of the bag has extra room to allow the insulation to ‘loft’ in the top of the bag.
To save a little weight the Quantum range of bags are 217cm long, rather than the usual 220cm. Also they are 75cm wide at the shoulder when some bags are 80cm wide. All this adds up to make this bag extremely light at just 732g, plus
18g for the stuffsack.

On the hill
The Cumulus Quantum 350 packs down amazing small, making it ideal for light backpacking trips. Pull the bag from the stuffsack and it instantly feels soft, while the down soon lofts to make this feel very cosy. There is a good, well-filled zip baffle down the length of the side zip. I did snag the zip a few times though. There is a shoulder baffle on the front of the bag, but this does not extend around the back as most shoulder baffles do and it does not have any drawcord adjustment. The hood fit was okay, but others are better. Overall I did not think the head and shoulder area was as good as other bags. The shorter length of the bag was not a major problem for my 5ft 11½in frame, but I did notice that the width was a little tight, which resulted in compressed insulation at my elbows. Of course those with a slimmer build than me will find the width ideal.

In the lab
At 9.3TOG / -6.5 deg C the results of our lab test closely matched the temperature rating of the Cumulus Quantum 350.

Size 217x75x50cm
Outer fabric Pertex Quantum
Inner fabric Pertex Quantum
Fill weight 350g of 96/4 white Polish goose down
Fill power 870
Lower comfort temp rating -6 deg C
Trail temp rating -6.5 deg C
Packed size 24x15cm; 18x15cm compressed
Weight bag 732g; stuffsack 18g
Made in Poland
Stores across UK 13
Stockist details tel. (0161) 929 1782;


The weight and packed size of the Cumulus Quantum 350 are superb. However, the zip snagged more easily than others; hood and shoulder baffle design not as good as other heavier bags. Overall, it’s great for lightweight backpacking but other bags have enhanced performance

Review by Graham Thompson
First published in Trail magazine Spring 2010