Hispar 400 Down Sleeping Bag: K Series

Warmth to weight taken to the limit with our 'K Series' version of this mountain lightweight for cool conditions. Ideal for fast ascents and quick travel.
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.
-9°C / 15.8°F
For clothing, weight is for size: M. For sleeping bags, weight changes with selected length/width. N.B. there may be some variation in the weights of finished products.
655g / 23oz
Hispar 400 Down Sleeping Bag: 'K Series'

By far the best warmth to weight ratio of all the bags tested
Chris Townsend, TGO Magazine's test of 3 season sleeping bags.



  • PHD 'K Series': Ultimate warmth/weight performance
  • Unique PHD 1000 fillpower Down
  • Outer: Ultrashell water-resistant fabric. An excellent balance of weight, water-resistance and breathability
  • Inner: Superlight 10X fabric. Down-proof, wind proof and super soft
  • Box-wall construction for max loft
  • Short zip protected by double draft tubes
  • Pack size: 20 x 34 cm†
  • Straight-wall baffles for lightness
  • Side block baffles to prevent down shift
  • Extra down channels along each side ensure side insulation
  • Oval footpiece to fit naturally to feet and avoid pressure
  • Mummy hood draws up close around head
  • Collar seals in warmth at neck
  • Stuff sac with mesh storage bag
  • Options:
    • Waterproof Dri-LX outer fabric shell (+250g)‡
    • Slim, Wide and Extra Wide widths*
    • Short, Long, and Extra Long lengths*
    • Full zip (left or right)
    • Further customisation available via our Design Your Own Sleeping Bag service

†Please note: We make our stuff sacs big enough to allow fairly easy stuffing rather than reducing the bags to the tightest minimum.

‡Please note: The optional waterproof Dri-LX outer provides an extra seam-sealed outer shell to the bag. While a shelled sleeping bag is not designed to be used alone in heavy rain (the hood area is open to the elements) the shell does protect the bag when it is used outdoors without a tent.

*Please note: For all length or width options, we change the amount of downfill to keep the warmth (TOT) the same.


This K Series product has been created for one single reason, to take warmth-for-weight performance to the limit of what's possible. Unique 1000 down, super-light materials, and specific design features mean that the word Ultralight now applies to this wide range of gear that will take you to the Poles as well as on a Sahara Marathon. More on the K Series...

Ultralights for the mountains is what we have always called Hispar sleeping bags and even with the new K Series versions it's hard to find a better way to describe them. Perhaps 'Ultralightest' would be closer if it wasn't such an awful word.

The combination of this bag's design with the superlative quality of our 1000 down and our new fabrics, Ultrashell and 10X, almost send the Hispar K range off the scale for warmth/weight performance.

  • The straight-wall baffle system (as used on the Minimus) is the lightest available.
  • The close-fitting mummy hood borrowed from the high-performance bags brings a snug protective feel.
  • A short zip with a double draft tube is standard on these bags (a zip is necessary with a mummy hood), and side block baffles have been inserted to prevent down shifting between top and base.
  • The outer V baffle at each side protects the side seams and increases the inner/outer differential to allow the down full loft.
  • A simple internal collar completes the technical specifications.

The weights of the Hispar K bags are graphic evidence of the effectiveness of this specific design. With the added performance of our 1000 down these bags deliver the greatest possible warmth per gram.

The optional waterproof Dri-LX outer provides an extra seam-sealed outer shell to the bag. While a shelled sleeping bag is not designed to be used alone in heavy rain (the hood area is open to the elements) the shell does protect the bag when it is used outdoors without a tent, for example in a snow-hole or under a tarp.

Dri-LX (weight: 64 gsm)

At just 64gsm, Dri-LX is our lightest 2-layer breathable waterproof rip-stop nylon fabric. Its remarkably low weight not only makes for a lighter load, but also reduces pack size. Its excellent waterproofing qualities are in part due to how it can be taped at the seams to create a waterproof shell for sleeping bags and clothing.

Ultrashell (weight: 40 gsm)

One of the lightest of PHD's coated materials. This ripstop nylon provides complete wind block and good water resistance at minimal weight. Ultrashell gives an excellent upgrade to performance with very little weight penalty.

Ultralight 10X fabric (weight: 26 gsm)

10X, PHD's first 10 Denier Fabric. 9,000 metres of the yarn used to weave 10X weighs just 10g, that's about the same as a £1 coin! For all its thinness 10X is amazingly downproof and with reasonable care will go on giving you good service for years.

Sleeping bag zips

  • No zip: The standard design on our lightest bags with open hoods. The simplest/lightest system which is a must for adventure racers. Up to 140gm (5oz) lighter than a full zip with draft tube.
  • Full zips: Full zip bags ventilate well, so they can be used over a wider range of temperatures.
  • Short zips: Short zips are lighter and pack smaller than full zips. A short zip & draft tube is up to 85gm (3oz) lighter than the full version.
  • Our full briefing on sleeping bag zips.

1000 fillpower down

This rarest of all downs we reserve for the K Series. European goose down of unique quality. 1000 provides the highest warmth-for-weight performance possible from down. More on our down insulation.


This bag has an insulating straight wall baffle system throughout (no straight-through stitching). Straight wall is the lightest of all baffle systems. In cross section it looks like this:

Side V channels, and double draft tubes behind the zip optimise insulation.

More on sleeping bag construction.

"Phenomenally light for the warmth it provides. Zero cold spots. The neck baffle forms a collar that would impress a Tudor queen, meaning no draughts here. And whilst the bag is light, no corners have been cut with the shell, which is tough and proved water-repellant after a damp night surrounded by wet kit."
Lucy Wallace, 'Best Buy' in TGO Magazine's Comparative Review of Women's Winter Sleeping Bags.

"Amazing warmth for the weight. Very light and very warm the K Series Hispar 400 bag has by far the best warmth to weight ratio of all the bags tested. If you want the maximum warmth for the least weight...this is the bag to choose"
Chris Townsend, TGO Magazine's test of 3 season sleeping bags.

"I used my Hispar 400K on a three week trip to Everest Base Camp via Gokyo Ri and over the Cho La pass. With 18 nights in varied temperatures down to -1c at our tented camp at the base of Kala Patthar I can safely say this is a brilliant bag. Just 875g, mine is long and has a full length zip, it performed exceptionally well and for such low weight. Whilst not a test down to the rated -9c I am a 'cold' sleeper and I know I could have gone further down than -1c in comfort, trust me for me that is a testament to the bags warmth. Thank you PHD."
Rob Pinate

The reviews below relate to standard Hispar 400, which is 115g heavier

"This has to be the best sleeping bag I've ever used in every respect. It's warm as a very warm thing (good to -9). It's not cheap but then you get what you pay for when it comes to sleeping bags. PHD are a very small company but they beat the socks off the big guys."
Phil Newby, registered BAIML International Mountain Leader.

"I have a new Hispar 400 which is proving to be very good indeed."
Tim Rodgers.

"I have one of your Hispar Bags and think they are amazing."
Richard Bishop.

"In September, I had the opportunity to use my Hispar 400 bag in Iceland. The bag was so warm that I didn't need to close the zipper!"
Volker Junge.

"Having ordered a Hispar from you last month and testing it wild camping in North Wales to around -2 degrees, I have to admit that the bag is brilliant! I was toasty while my climbing partner shivered! Thank you for the excellent gear and hopefully my down jacket will be falling apart soon so I can justify replacing it with one of yours!"
Alistair Ross.

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