Ultra Down Vest: K Series

Our lightest sub-zero down vest. A 'K Series' product. Warmth to weight at the limit of possibilities for extra-keen lightweight backpackers and mountain racers. Now also available in custom sizes.
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.
130g / 5oz
Ultra Down Vest: K Series

For Alpine and winter stuff we use PHD's Ultra Down Vests. These are the best lightweight kit on the market.
Phil Newby, registered BAIML International Mountain Leader.



  • A PHD 'K Series' Product: Ultimate warmth / weight performance
  • PHD's Unique 1000 fillpower down
  • Sheer-light 7X  fabric
  • Full width front handwarmer pocket
  • Stitch-through for lightness
  • Elasticated side panels for closer fit
  • Small zipped security pocket
  • Full length lightweight front zip
  • Insulated under-baffle with wrap-over chin guard
  • Elasticated side hem
  • Drop-tail back
  • Stuff sac
  • Pack size: 10 x 18cm*
  • Options:
    • Water-resistant Hypershell (Red or Black,  + 10g, +£16)
    • Stud on hood with Lycra edging: Adds 35grms

* Please note: we make our stuff sacs big enough to allow fairly easy stuffing rather than reducing the vest to the tightest minimum.


Also available in custom sizes. We make clothing to order, so if you’re not a standard size we can make it to fit. To order a non-standard custom size, select the Custom Sizing tab and choose the body width and body length sizes that work for you. A custom size takes us a little longer (typically two weeks longer) to make and, because it’s personalized, it’s non-returnable and our customer loyalty scheme can’t be applied.

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...

Our lightest sub-zero down vest is a genuine piece of mountain gear whose warmth will surprise you. The 7X inner fabric reduce the weight to a minimal 130gm. Warmth to weight at the limit of possibilities for extra-keen lightweight backpackers and mountain racers.

Pared down design as for all the Ultra range, elasticated side panels for a closer warmer fit, waist-level front pockets, zipped inner security pocket, and a drop-tail back.

The outer fabric can be upgraded to water-resistant Hypershell to elevate the performance at just a very minimal increase in weight.


Ultralight 7X fabric (weight: 22 gsm)

7X is our new sheer-light 7 denier fabric. An exquisitely fine rip-stop nylon, 7X is incredibly light, highly wind-resistant and has first-rate down proofing. This fabric helps us create the very lightest of gear in the PHD range. Of course the lighter the fabric the lighter the sleeping bag or down clothing, and the less space it takes up in your rucksack. This fabric is so light it actually helps to allow even greater lofting of the down too.

Water-resistant HyperShell fabric (weight: 28 gsm)

HyperShell is PHD’s exceptionally lightweight waterproof coated fabric. This remarkable ripstop nylon provides complete windblock and good water resistance at a breath-taking weight (28 gsm). HyperShell protects the down from condensation drips found typically in tents, tarps and snow-holes, but its very low weight allows greater lofting of the down and a smaller pack size. Hydrostatic head: 1000mm.

Note: unlike some other so-called 'proofed' fabrics, HyperShell does not rely solely on a DWR (durable water repellent) coating. Although it has a DWR coating, more importantly it has a breathable and permanent PU coating applied on the underside of the fabric that cannot be abraded through daily use, so performance is maintained over many years.

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.

Comments are for previous version of this vest, which weighed the same, but didn't have a water-resistant outer fabric

"For Alpine and winter stuff we use PHD's Ultra Down Vests. These are the best lightweight kit on the market."
Phil Newby, registered BAIML International Mountain Leader.

"I bought an ultra down vest from you a couple of months ago and used it at Easter when I was camping in the Cairngorm's. I was really impressed how light and yet warm it was, despite the temperature dropping to -10 overnight and there being a couple of foot of snow!"
John H.

"Just got my Ultra Vest. I wanted to say a big 'thank you' for designing such a fantastic piece of kit. It just felt 'right' as soon as I took it out of the parcel. I put it on (on this chilly July morning ...) and I felt immediately warmer. It is the most astonishing piece of kit I've ever owned (and I have an awful lot of stuff, let me tell ya). Beautifully designed, perfectly executed (not a stitch out of place). It's just breathtaking."

"So small and light that you cannot possibly not have it with you at all times! It is comfy and, when, at first I put it on I could not believe that it would keep me warm. How wrong I was. It is unnoticeable as a physical layer but highly noticeable as a warm layer. Peter Hutchinson has become a god of light and warm clothing in my book."
Jeremy Hastings, Islay Bushcraft.

"I've been meaning to write to say what a tremendous bit of kit this Ultra vest is. I have to say the warmth to weight ratio is sensational. Top quality bit of outdoor clothing and it's been a pleasure to deal with your company."
Mark H.

"Thanks for the Ultra vest ... a really amazing piece of kit. This must be pretty much the best warmth/weight ratio insulation piece in the world. I was glad to see your quoted weight matched the actual weights precisely. This garment is set to become an instant classic."
Alex Haxeltine.

"Just a quick note to say I have just completed the Marathon des Sables and found your new ultravest to be the perfect wear for the colder mornings."
John Moorhouse.

"I couldn't believe the warmth to weight performance of that little beauty [the Ultra Down Vest]. It fitted my requirements perfectly. Many thanks and congratulations on making such fantastic products."
Edward Fowler.

"Stuffs tiny. I'm wearing it now as the heating is being weird, lovely and warm and silky."
'Kesh' on Live for the Outdoors forum.

"I am so pleased with it! Tested that very evening ... I was like toast, and again the vest came up trumps whilst out in the woods last weekend. Once again thank you very much for a superb bit of kit!"
Andrew Jones.

"In a way it's a shame that the Ultra vest is as nice as it is! In the interim I'd ordered myself a Mountain Hardwear Below Zero jacket but I'm afraid that it feels second rate compared to the PHD vest. I fear that I'm going to have to return the MH and get myself a Hispar!"

"Ultra Vest arrived today. It is a sensational product. Thank you for it. It was worth waiting for. Please thank the artist who made it for me!"
Adam from Hobart, Tasmania.

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