Delta 350 Down Sleeping Bag

Very light, packable bag. Neck length for lightness. Overnighter on a fast mountain climb, or a high ridge traverse.
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.
-5°C / 23°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.
600g / 21oz
Delta 350 Down Sleeping Bag


  • Neck-length bag
  • Water-resistant Ultrashell outer fabric. An excellent balance of weight, water-resistance and breathability
  • Superlight MX inner fabric
  • Exceptional 900 fillpower European Goose down
  • Box-wall construction for maximum loft
  • Water-resistant Ultrashell inner panels at shoulder and foot
  • Stuff sac with clip loop
  • No zip for lightness
  • Pack size: 17 x 28 cm†
  • Stretch cord with cordlock at the shoulder
  • Reflector strip for night location
  • Clip loop to secure sleeping bag while sorting out
  • Ovoid shaped footpiece to fit naturally to feet and avoid pressure
  • Mesh storage bag
  • Colour: Burnt Orange & Charcoal
  • Options:
    • Long length*
    • Wide width*
    • Waterproof Dri-LX outer fabric shell (+200g)‡
    • Full zip (left or right) with double draft tube
    • Full water-resistant Ultrashell fabric inner
    • Zip-on extender to form a sleeping bag for two (requires full length zip to be chosen at the same time)

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 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.


A hoodless sleeping bag of amazingly low weight and bulk, which opens up new possibilities. Suitable as essential kit on a planned extreme ascent through to confidence-boosting backup in any mountain country:

  • Hiking the Pyrenees, not sure where you’ll sleep? The Delta 350 will take care of it
  • Multi-day ascent in Patagonia or Alaska? Customise the Delta 350 with a full water-resistant Ultrashell inner, and with a width extender to turn your bag into a double
  • Alpine-style ascent in the Himalayas? The Delta 350 can take you high, twinned with the right clothing

The water-resistant Ultrashell outer protects from condensation, and Ultrashell panels inside protect from damp. The reflective strip for night location and the clip loop to organise on a belay ledge are part of a superb features list.

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.

The optional zip-in Width Extender turns your single bag into a double.

Sleeping bag width extender

PHD's fully insulated width extender converts a single Delta sleeping bag into a bag for two. It's attached to the bag by its full length zip and is fully insulated by the host bag's own draft tubes. The insulation level matches that of the host bag to ensure consistent warmth. An extender requires a full length zip to be chosen and can only be ordered at the same time as the bag.

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.

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.

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.

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.


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

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).