This system is very similar to the one already used successfully on Broad Peak (see Case Study), but it advises a much warmer sleeping bag. The Hispar 600 only weighs a little over 200g (7.1oz) more than the bag used on Broad Peak, but it gives a greatly increased margin for mishap or bad weather, a necessary precaution on a mountain as remote as Vinson.
As climbing kit, the Xero suit has been to 8000m summits and is rated for -40°C (-40°F). Here it doubles as the night-time booster for the Hispar 600 bag. With the suit worn inside, the performance figure for the bag increases from -21°C (-5.8°F) up to -47°C, as in System 1, warm enough for comfort and safety in the Antarctic summer. The suit is simpler to use than the separate clothing shown in System 1, but less versatile.
: The 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.