Sleep systems

Cold Racing: System 1

Carry the minimum weight and bulk on your race along with the confidence that this system will provide the warmth you need. The Yukon Jacket is a proven performer for low temperature racing. Then at night wearing your down clothing inside the Hispar 600 moves the performance rating right down to -36°C. Yet the Hispar bag weighs nearly 500g less than a standard lightweight bag rated to -36°C and packs down to about two-thirds the volume. The Hispar 600K version 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.
-36°C / -32.8°F
Schematic representation of Sleep System. Actual components differ.


  • System Products:
    • Main Sleeping Bag: Hispar 600 (Sleep Rating: -21°C / -5.8°F)
    • Plus Items: 
      • Yukon Down Jacket
      • Rondoy Down Trousers
      • Minimus Down Socks*
  • Full System Sleep Rating: -36°C (-32.8°F)
  • Sleeping Bag Weights:
    • Hispar 600 Down Sleeping Bag: 1040g (36.7oz)
    • Standard lightweight Sleeping Bag to achieve Full System warmth: 1525g (53.8oz)

Note: The Alpine Ultra Half Bag can be used inside the Hispar bag instead of the Rondoy Trousers and Minimus Socks. The performance rating is the same.


This system provides night-time warmth down to -36°C, a proven cold weather racer's jacket for daytime wear, and down trousers for extreme weather or camp use. The normal sleeping bag for these kinds of temperatures weighs between 1.5 and 2 kilos by itself, and you'll still need the down clothing. With sleep systems you can have it all and cut a large slice of the weight and bulk from your pack.

K Series: The Hispar 600K Sleeping Bag is available in the K Series. The exceptional loft of 1000 down reduces the weight to just 885g (31.2oz), creating a unique sleeping bag that still fulfils its -21°C (-5.8°F) rating at under a kilo pack weight.

Review relates to Hispar 600 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.

Review relates to Yukon Down Jacket

"Many thanks for the jacket that you supplied me for the Yukon Arctic Ultra. [It] performed perfectly in temperatures down to -35°C. The light weight and small size was also a huge help and helped me gain second place in the race. I ... am now the second fastest person over the course and the fastest European."
Dr Stuart Gillet (wearing a prototype Yukon jacket).

Review relates to Rondoy Down Trousers

”The lightest 'big mountain' down legwear that PHD has produced. They use 950 fill down, water-resistant Ultrashell face material and have full-length side-zips for ease of use. Serious cold weather trousers.”
OutdoorsMagic Review.

Review relates to Minimus Down Socks

"The solution to cold feet."
Mike Smith, on Trip to Greenland's 'North Liverpool Land', April/May.

Sleep system components

Works well with
From £900.00 1040g -21℃
Mountain lightweight for low temperatures and high peaks. Ideal for fast ascents and quick travel.
From £585.00 400g -20℃
Our lightest big mountain and high-altitude trekking down-filled trousers. Now also available in custom sizes.
From £174.00 90g
Unbelievably light down-filled sock for warm feet in cold tents.