Diamir 900 Down Sleeping Bag

High-specification expedition bag, cut roomy enough for stashing kit and for comfort at altitude.
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.
-32°C / -25.6°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.
1740g / 61oz
Diamir 900 Down Sleeping Bag

I highly recommend this bag to anyone looking for a lightweight, compressible, very warm winter bag that looks like it will last for many seasons to come.
Sam Feuerborn



  • Exceptional 900 fillpower European Goose Down
  • Water-resistant Drishell outer fabric
  • Superlight MX inner fabric
  • Box-wall construction for max loft
  • Inner water-resistant panels
  • Full length zip protected by double draft tubes
  • Pack size: 25 x 44cm†
  • Mummy hood draws up close around head
  • Wide 3D Collar seals in warmth at neck
  • Trapezoid baffle system for ideal down control
  • Special baffle section stabilises down over chest
  • Extra down channels along each side ensure side insulation
  • Side block baffles prevent down shift
  • Drishell inner panels at head to protect against breath soaking the down
  • Drishell panels at inner foot to cope with damp feet/footwear
  • Footpiece: ovoid shape to fit naturally to feet and avoid pressure
  • Black inner for quick drying
  • Stuff sac with large mesh storage sac
  • Colour: Red and Gold
  • Options:
    • Zip location: left or right
    • Short or Long lengths*
    • Waterproof HS2 outer fabric shell ‡
    • 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 bag to the tightest minimum.

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

‡Please note: The optional HS2 outer is a complete extra outer shell, with seams taped for weatherproofness. The extra layer of fabric adds considerably to the weight and bulk of the basic bag. It increases the weatherproof qualities of the bag in mountain or arctic situations, but it is not a substitute for a proper bivvy bag when sleeping out in the rain.


This Diamir down sleeping bag takes specialised mountaineering and expedition bags to a new level with the use of PHD's exceptional 900 fill power down and inner Drishell panels at head and foot. The Diamir represents the benchmark for expedition down sleeping bag standards.

Cut roomy enough for comfort, and for stashing vulnerable kit overnight with you, this bag is well suited to long periods in remote camps. The trapezoid baffles provide a lightweight method of achieving excellent down control, aided by vertically-oriented chest baffles that prevent any chance of down migration.

  • The Drishell outer is highly water-repellent and helps to keep the down dry and lofting.
  • The Drishell inner panels in the hood and foot area also protect the down.
  • A large 3D shaped collar, side V channels to insulate the side seams, double draft tube behind the zip, and closely-boxed foot section form part of a formidable list of technical specifications.

Pictures show Diamir 1200, Diamir 900 is a little slimmer.

Water-resistant Drishell outer fabric (weight: 54 gsm)

Ripstop nylon with an ultralight coating: achieves total windblock, along with high breathability and superior water resistance. Superbly efficient for a very light overall fabric weight.

Superlight MX fabric (weight: 32 gsm)

A mini-ripstop nylon with excellent tear strength, MX is the pick of the superfine 15 denier downproof materials. We have tested lighter fabrics, but most have had significant drawbacks, while our confidence in MX is based on several years of extensive use in both our ultralight and our high mountain gear.

900 Fillpower Down

European goose down of very high quality. A truly excellent down with large clusters, consistent quality and lively long-term performance. More on our down insulation.


PHD's trapezoid baffle system is used throughout. This is the best of the technical baffle systems, combining excellent down control with low baffle weight. In cross section the baffle system looks like this:

The design has a close-fitting down-filled mummy hood, and side V-channels which ensure all areas of the body are insulated. The baffles over the chest are vertically aligned, which stops any horizontal shifting of the down caused by arm movement during the night.

More on sleeping bag construction.

Proofed inner panels

Proofed fabric (Drishell or Ultrashell) panels are included inside the hood and foot areas of the bag to help keep the down dry. In very cold temperatures your breath can cause ice to form around the face opening, which may soak into the down as it melts. The panels at the foot end are to protect the down if you get into your bag with wet socks (or in extreme situations with your boots on).

Waterproof HS2 outer fabric (weight: 88 gsm)

HS2 is PHD's high-spec 2-layer ripstop for waterproof outers on our down. It is light enough to be the optional taped shell on our sleeping bags and tough enough for expedition use in our Omega clothing. HS2 is completely waterproof (when the seams are taped) and offers excellent breathability.

"I spent over 90 nights in the PHD Diamir 900, and not a single one involved a shiver while sleeping. I slept in my unheated van at trailheads in the San Juans before ice climbing and ski trips; in tents in the mid-winter desert; under a blanket of stars on multi-day ski tours; and everywhere in between.

The Diamir 900's 900 fill down had an unbelievably high weight-to-warmth ratio, as one would expect. Couple that with an almost perfect fit and a waterproof outer, and this bag proved to be perfect for this past winter and for future cold weather expeditions.

I highly recommend this bag to anyone looking for a lightweight, compressible, very warm winter bag that looks like it will last for many seasons to come."
Sam Feuerborn.

"Thank-you for the superb sleeping bag."
Robert De Mey

Works well with
From £750.00 725g -30℃
A high-altitude mountaineering jacket that's incredibly light for its capabilities....
From £479.00 400g -20℃
Our lightest big mountain and high-altitude trekking down-filled trousers. Now also...
From £173.00 170g
High-altitude expedition socks. Light, compressible and comfortable. For warmth in high...