Fire & Ice Ultra

Billed as Iceland’s Toughest Foot Race – and confirmed by those who’ve done it as one of the World’s toughest – the Fire & Ice Ultra takes 6 days to cross 250km of volcanic ash, glacial rivers, barren rock, grassy meadows, and everything else the Icelandic terrain can possibly throw at you.

Although the race takes place in summer, it can still get cold at night. Competitors need to carry their kit with them so, as always, a balance needs to be struck between what you’re reasonably prepared to carry and the warmth you need.


Down Sleeping Bag selection

The kit list requires a sleeping bag, with or without liner, which is capable of withstanding temperatures of 0°C. The most obvious choice from our main range therefore would be the Minim 400 or 400 K, with a TOT (Typical Operating Temperature) of -5°C.

However, the Minimus/Minimus K has a TOT of 5°C, and the Superlight bag from our Design Your Own series can be specified with a TOT as low as 4°C, so provided they’re combined with suitable down clothing, these bags could form the basis of an exceptionally light Sleep System rated to around 0°C.

S-bag TOT (Min Temp) Weight Packed size
Hght x Diam (cm)
°C  °F gm oz 
Minimus 5 41 465 16 21 x 13
Minimus K 5 41 380 13 21 x 13
Minim 400 -5 23 670 24 28 x 17
Minim 400 K -5 23 585 21 28 x 17

Additional points:

  1. TEMPERATURE RATING: Put simply, these are the temperatures at which you should be able to get a night's sleep in normal circumstances. For fuller details about the TOT rating see this Technical Briefing.
  2. LINERS: A liner will add to the insulation, but as always there is a trade-off between the extra weight and bulk, and the warmth you gain. Silk liners add roughly 2°C but only weigh around 140g so they’re a popular choice. If you’re particularly concerned about cold, our K Series Filler Bag is 100g heavier than that but will add 10°C.
  3. CLOTHING: Thermal baselayers obviously help to keep you warm, and lightweight warm layers such as our Wafer clothing boost the performance of the bag considerably. See the Clothing section below for more details.
  4. FABRIC OPTIONS: The Minim 400 and 400K come with M1 and MX outer fabric as standard, but are also available with Drishell/Ultrashell. These options are highly wind/water resistant but do not add significantly to the weight of the bags: Drishell adds about 40g, Ultrashell adds about 18g. The Superlight comes in exceptionally lightweight 10X (or even 7X, our lightest ever fabric), but is also available in Ultrashell.
  5. ZIPS: These bags are all designed with a wide enough opening to work without zips; zips are an option, but competitors often don't ask for one, to minimise weight. A short zip with draft tube adds about 50g (2oz), a full zip and tube adds about 110g (4oz). The Superlight is also available with a venting foot zip, which adds about 10g (⅓oz). Zips also add to the packed size.
  6. PACKED SIZE: PHD stuff sacs tend to be on the loose side, for ease of stuffing. All these bags can be compressed further in your pack.
S-bag TOT (Min Temp) Weight Packed size
Hght x Diam (cm)
°C  °F gm oz 
Minim 400 (Drishell) -5 23 710 25 28 x 17
Minim 400 K (Ultrashell) -5 23 603 21 28 x 17

Clothing selection

The kit list specifies a warm mid layer, for cold days or at camp in the evening. The Wafer Jacket provides warmth down to round about freezing point, but weighs just 190g; if you really tend to feel the cold though, then the Ultra K Jacket or Pullover have also proved popular on the Fire & Ice, offering a fantastic level of warmth and still a very low weight: they have a TOT of -5°C but are nevertheless just 240g or 225g respectively.

Some opt to take a light synthetic gilet too. Like the Wafer clothing, the Sigma Vest has a TOT of 0°C but, thanks to its synthetic Primaloft insulation, it’s far less moisture sensitive than down: you can wear it to boost core body warmth when running in the cold without being concerned about perspiration saturating it.

All the above clothing can be worn inside a sleeping bag on colder nights; if Wafer Trousers and Wafer Socks are also worn to create a Sleep System, the performance will be quite significantly enhanced, despite a weight gain of only 175g. And please, don’t underestimate the importance of the socks! Cold feet are a quick and simple way to an uncomfortable, interrupted night (and a sluggish, groggy next day).

The next Fire & Ice Ultra starts on 29 August 2022:

Photo by Paul Morris.