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.
: 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.