Sleep systems

Trekking Peaks: System 3

The simple Filler bag boosts the Hispar 500 to -25°C performance in this system. But it can also double up with the Rondoy jacket to take the rating to below -30°C, as well as working as an emergency item on the climb.
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.
-25°C / -13°F
Schematic representation of Sleep System. Actual components differ.


  • System Products:
    • Main Sleeping Bag: Hispar 500 (Wide) (Sleep Rating: -15°C / 5°F) Weight 915g/32oz.
    • Plus Items:
      • Rondoy Down Jacket
      • Filler Down Sleeping Bag
  • Full System Sleep Rating: -25°C (-13°F)


The Hispar 500’s -15°C performance might be enough for your high camp on its own. But no need to take the risk of a temperature drop. Slip the Filler bag inside and you’ll increase the rating to -25°C. And if that’s not enough, double the Filler down to make a halfbag for your legs and wear the Rondoy jacket as well. 

For the ascent the Rondoy jacket itself is a superb mountain lightweight offering great warmth for its weight (the K series Rondoy weighs only 500g!). And if you want an emergency backup item on summit day, the Filler bag at 240g makes a lightweight bivvy or converts easily into a makeshift halfbag (down socks would add a touch more comfort to either useage).

K SeriesThe Hispar 500K Sleeping Bag (Wide) is available in the K Series: performance is the same, but the exceptional loft of 1000 down reduces the weight of the bag to an amazing 855g (30oz).

Review relates to Hispar 500 Down Sleeping Bag

"The lightest bag tested yet warmer than some ... The Hispar 500 really does deserve the description 'Ultralight' ... The loft really is astonishing for such a lightweight bag ... the Hispar 500 is my favourite of the bags tested."
Chris Townsend, Winter Down Sleeping Bags test, TGO Magazine.

Review relates to Rondoy Down Jacket

"The jackets were incredibly warm and light, equally suited to ensure we were warm when climbing and even when static, melting snow, in the advance camps."
Jonathan Phillips, Imperial College, Obra Valley Expedition (GARHWAL HIMALAYA, INDIA).

Review relates to Filler Down Sleeping Bag

"It is a pleasure, when you know the temperature is dropping, just to slip into another bag and double the warmth factor."
Sam Cook.

Sleep system components

Works well with
From £828.00 915g -15℃
Mountain lightweight for cold conditions. Ideal for fast ascents and quick travel.
From £830.00 620g -20℃
A lightweight mountaineers' and trekkers' Jacket for the 6000m Himalayan peaks, the high Andes, and the Winter Alps. Now also available in custom sizes.
From £486.00 240g +15℃
A lightweight liner that boosts your sleeping bag's warmth by 10°C. On its own, the lightest of sleeping bags. A PHD 'K Series' product: warmth to weight at the limit of possibilities.