Alpine Ultra Down Jacket: K Series

'K Series' version of our lightest climbers' down jacket with chest pockets and optional helmet-sized hood. Lighter and warmer than fleece. Warmth to weight at the limit of possibilities. 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.
-10°C / 14°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.
295g / 10oz
Alpine Ultra Down Jacket: K Series

Packs to nothing.
Petesy (a.k.a. Peter Macfarlane).



  • A PHD K Series product: Ultimate warmth / weight ratio
  • PHD's Unique 1000 fillpower down
  • Water-resistant Ultrashell outer fabric. An excellent balance of weight, water-resistance and breathability
  • Superlight 10X inner fabric. Down-proof, wind proof and super soft
  • Stitch-through for lightness
  • Front lightweight zip with internal draft baffle
  • 2 chest pockets (lightweight zips) above harness level
  • 1 internal security pocket
  • Elasticated side panels for closer fit
  • Lycra cuff
  • Double-exit shock cord hem
  • Drop-tail back
  • Reflect for night location
  • Clip loop for securing
  • Stuff sac
  • Packed size: 13cm x 21cm*
  • Option:
    • Down filled superlight zip-on hood

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


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...

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, choose your body width, and then the body/arm lengths, shorter or longer, 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.

The original Alpine Ultra has been acclaimed as the perfect Alpine Jacket, but it's won friends in the Himalayas too as the ideal example of light and warm. Now this K Series version is just as warm and a full 45gm lighter with all the features and capability of the original. Enough said.

Facing an early morning start, a cold wind high up, even an unexpected bivvy. Whenever you're going to need extra warmth on your peak, it doesn't come any lighter than the Alpine Ultra. It's lighter than fleece, much warmer, packs a lot smaller and has a 100% windproof outer too.

Chest pockets and a large (optional) hood allow harness and helmet use. And together with elasticated side-panels, for a closer, warmer fit, great performance is guaranteed.

Note: The optional hood needs to be ordered at the same time as the jacket.



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.

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.

"Just want to say how impressed I am with the Alpine Ultra K series jacket. I took it to Norway this year with temps down to -15 degC, without the wind chill on top, and it was perfect. Packs as small, possibly smaller, than my waterproof jacket, lofts quickly when unpacked and is amazingly warm. I kept it in my pack, or attached to my harness (it's that small & light), and the first thing I did at every belay was put it on; bliss."
Andy Syme.

Comments below relate to standard Alpine Ultra, which weighs 50g more

"Packs to nothing."
Petesy (a.k.a. Peter Macfarlane).

"It's the perfect alpine downie - 330g and rated to -10 degrees - it blows the competition out of the water. Whilst the weight is awesome, you also get a tiny packed size out of it meaning that your down jacket won't eat up half your backpack space so you can go with a small backpack (20L) and keep a light and fast rhythm to your climbing."
Jon Griffith.

"I used the Alpine Ultra Jacket as a belay jacket and emergency outer layer in the Indian Himalaya - I found it to be excellent. It's lighter and packs down smaller than any comparable jacket, and its warmth to weight ratio is second to none. There is no other jacket that I would've preferred to have with me."
Virgil Scott - Imperial College Reru Valley Expedition (Zanskar Himalaya, India).

"Thank you for the fantastic equipment. Everything (including the Alpine Ultra Jacket) was above and beyond what was required and fended off the elements perfectly."
Graham B., on a trip to Aconcagua.

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