Mountain Equipment
Helium 400

In Stock Left Zip: Cosmos Regular
MSRP £220.00
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Last Updated: 12/11/2012
Glossary - Fill power close

Fill power is a measurement used to quantify the ability of down to resist compression, known as its loft. The higher the fill power, the more space the down occupies and the more effective it is as an insulator. Higher fill power down is hard to source and therefore expensive, it does however offer significant weight savings for gram-counting alpinists.

In the outdoor industry fill powers tend to start at around 650 and currently go up to 850 (900 does exist but is rare and mostly needs to be 'handplucked' from live birds). The down's origin is also sometimes given, most 'European' down comes from Hungary and the Ukraine and tends to be better quality that Chinese sourced down. The species may also be given but is not strictly speaking informative. The best goose down will outperform the best duck down, but good duck down will outperform poor goose down.

In addition to the fill power figure, there is sometimes a percentage quoted, eg '85% down' or '85/15 down'. This refers to the ratio of pure down to small feathers used. Higher feather percentages tend to be found on less technical products where down is padded out with feathers which cost less and offer more rigidity to compensate for the lower loft, however almost all products contain some feathers to increase the durability of the down.

International Down and Feather BureauIn the past a number of different competing systems were used to measure fill power. Today almost all outdoor manufacturers use the International Down and Feather Bureau's testing method (sometimes known as the US method). This involves pre-conditioning the down being tested with steam, which gives the best consistency for test results. It is then placed in a cylinder and stirred to maximise its loft, before its volume is measured in cubic inches after being compressed by an ounce weight to give the fill power.

Mountain Equipment Helium 400 Sleeping Bag

When space is in short supply, the Helium down sleeping bag is the perfect solution for a good night's sleep.

An incredibly light, versatile and packable sleeping bag well suited to backpacking and cycle touring, that will still happily cope with cooler nights during the spring and summer months.  The Helium 20™ outer shell is very light and highly breathable and the bag is stuffed with pure duck down with a minimum fill power of 700.

  • Weight: 855g
  • Fill Weight: 385g
  • Fill: 90-10 pure duck down with a minimum fill power of 700
  • Good night's sleep guaranteed: -5°C/23°F
  • Comfort: 3°C/37°F | Comfort limit: -3°C/27°F | Extreme: -19°C/-2°F
  • Packed Size: 24 x 20 x 17cm
  • Alpine Fit maximises thermal efficiency
  • Slanted box wall baffles throughout
  • Mid-level side seams
  • 5 baffle anatomically shaped hood
  • 4 baffle anatomically shaped and offset foot-box
  • Full length Gemini™ zip baffle and integrated collar with Lode Lock™ closure
  • Supplied with a waterproof roll-top stuff-sack and storage cube
  • Mountain Equipment is a member of the Fair Wear Foundation


Temp Rating
(EN 13537)
Rab Andes 1000 1625g 1000g 800 -17°C /-27°C /-49°C 195 x 75 x 57 cm
Rab Andes 800 1410g 800g 800 -13°C /-22°C /-43°C 195 x 75 x 57 cm
Rab Andes 800w 1395g 800g 800 -13°C /-22°C /-43°C 180 x 73 x 59 cm
Rab Ascent 700 1290g 700g 650 -2°C / -8.5°C / -27°C  
Rab Ascent 500 1090g 500g 650 1°C / -4.5°C / -22°C  
ME Womens Helium 600 1040g 555g 700 -1°C / -8°C  / -26°C
ME Helium 600 1070g 582g 700 -1°C / -8°C  / -26°C
Rab Neutrino 600 1030g 600g 800 -5°C / -12°C / -31°C 190 x 70 x 52 cm
ME Helium 400 855g 385g 700 3°C / -3°C  / -19°C
ME Womens Helium 400 855g 385g 700 3°C / -3°C  / -19°C
Rab Neutrino 400 820g 400g 800  2°C / -4°C / -20°C 190 x 70 x 52 cm
Rab Ascent 300 840g 300g 650  6.5°C / 1.5°C /-13°C  
Rab Neutrino 200 595g 200g 800  7°C / 2°C  / -13°C 190 x 70 x 52 cm
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