Sleep systems

8000m Peaks: System 2

Like System 1 this system is a serious weight-saver. Wearing the Xero clothing inside the Hispar 600 moves the performance rating right up to -47°C (the bag in the system is the Wide version to make sure that the down clothing can loft fully). Yet the Hispar bag weighs around 600g (21.2oz) less than a standard bag rated to -47°C and packs down to about two-thirds the volume. The Hispar 600K has even more impressive stats.
Typical Operating Temperature
Guideline minimum temperature. Sleeping Bag TOT: you should get a night’s sleep, under normal circumstances. Clothing TOT: you should feel warm enough, assuming low/moderate activity. Sleep System TOT: relates to full system. For more details, see our Technical Briefing.
-47°C / -52.6°F
Schematic representation of Sleep System. Actual components differ.
“This bag has an unmatched warmth/weight ratio.”


  • System Products:
    • ​Main Sleeping Bag: Hispar 600 (Wide) (Sleep Rating: -21°C / -5.8°F)
    • Plus Items:
      • Xero Down Jacket
      • Xero Down Trousers
      • Xero Down Socks
  • Full System Sleep Rating: -47°C (-52.6°F)
  • Sleeping Bag Weights:
    • Hispar 600 Down Sleeping Bag (Wide): 1154g (40.7oz)
    • Standard lightweight Sleeping Bag to achieve Full System warmth: 1760g (62.1oz)


This system is similar to the one already used successfully on Broad Peak (see Case Study), but it advises a much warmer sleeping bag. In theory, a Hispar 400 would do (the 400 has a similar rating to the Hispar Overbag used on Broad Peak), but the Hispar 600 only weighs a little over 200g (7.1oz) more and gives a greatly increased margin for mishap or bad weather.

As climbing kit, the Xero clothing is rated for -40°C, and the night-time boost it gives the Hispar bag takes the system rating up to -47°C, the same as System 1 with the Xero suit. The main difference is that the clothing in this system is in separate pieces. While the one-piece suit is simpler and often favoured for the highest peaks, separate clothing makes for a little more versatility and a wider usefulness for the kit on lower mountains.

K SeriesThe Hispar 600K Down Sleeping Bag (Wide) is available in the K Series. The exceptional loft of 1000 down reduces the weight to just 982g (34.6oz), creating a unique sleeping bag that still fulfils its -21°C rating at under a kilo pack weight.

This review relates to Hispar 600 Down Sleeping Bag

"This bag has an unmatched warmth/weight ratio ... The draft tubes undoubtedly provide the best insulation behind the zip of all the bags tested – not a trivial detail if you face harsh conditions."
from Carnets d'Aventures Magazine's test of 18 sleeping bags for cold conditions.

This review relates to Xero Down Jacket

"Peter Hutchinson makes probably the best down gear in the world and his Xero jacket has kept me happy (well as much as you can expect to be) deep into the minus 40 degrees."
Nick Lewis, Climb Magazine.

This review relates to Xero Down Trousers

"Your down trousers were lovely to wear in the hard wind outside the tent during our ski tour last week in the Swedish mountains."
Stefan & Susanne Grimfors.

This review relates to Xero Down Socks

"The Xero booties were great for sleeping in and I could also wear them inside my Sportivas for mooching around camp. All in all, perfect."
Nick Lewis, Antarctic Logistics & Expeditions.

Sleep system components

Works well with
From £877.00 1040g -21℃
Mountain lightweight for low temperatures and high peaks. Ideal for fast ascents and quick travel.
From £1,044.00 1250g -40℃
High-altitude expedition jacket. Light enough for the ascent, warm enough for when the mercury freezes. Now also available in custom sizes.
From £627.00 660g -40℃
Designed for fast moving expeditions to the highest levels or for any extreme cold weather venture where weight is at a premium. Now also available in custom sizes.
From £204.00 170g
High-altitude expedition socks. Light, compressible and comfortable. For warmth in high camps.