Rondoy Down Jacket: K Series

'K Series' version of our lightweight mountaineers' & trekkers' jacket. Box wall construction allows our unique 1000 fillpower down to loft fully. 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.
-20°C / -4°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.
500g / 18oz
Rondoy Down Jacket: K Series - in green Ultrashell fabric

The jackets were incredibly warm and light.
Jonathan Phillips, Imperial College, Obra Valley Expedition (GARHWAL HIMALAYA, INDIA).



  • A PHD 'K Series' product: Ultimate warmth-weight ratio
  • Down quality: Unique 1000 fill-power down
  • Outer fabric: water-resistant Ultrashell. An excellent balance of weight, water-resistance and breathability. 100% windproof
  • Inner fabric: Superlight 10X. Down-proof, wind proof and super soft
  • Box-wall construction for maximum loft
  • Pockets:
    • 2 waist level hand warmer pockets
    • 1 zipped chest pocket
    • 1 large zipped internal security pocket
  • Full-length two way zip protected by storm baffle
  • Internal draft baffle and beard guard behind zip
  • Elasticated inner back for snug fit
  • Adjustable velcro cuff tabs
  • Zip-off helmet hood with cord adjustment and volume reducer
  • Fleece-lined collar
  • Elasticated adjustable draw-cord hem
  • Clip loop for securing
  • Reflective tape (for night location) on chest and on the clip loop
  • Stuff Sac
  • Packed Size: 17 x 28cm*
  • Options: Blue, Green, Purple, Red and Charcoal colours

*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.

In the K Series the original Rondoy has been transformed into a streamlined big mountain jacket weighing around 500gm. 1000 down ensures the -20°C rating, the Ultrashell outer is proof against wind and damp, and the soft 10X inner adds a touch of comfort.

Two hand-warmer pockets at the waist, one chest pocket for stashing and quick access to your camera, a helmet compatible hood, and adjustable Velcro cuffs make this an exceptionally high-specification mountaineering Jacket.

The result is a superb lightweight you can take into big mountains with confidence (and a light pack).


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.

"Exceptional warmth to weight ratio. Fantastically rugged for the light weight. The down stays where it's supposed to, it lofts up quickly and after a 6 week expedition it still looks brand new despite rough ledge bivis and daily wear (no tear!)."
With Simon Smith on 6 week trip first ascending around the Tasilaq ford, East Greenland.

"Tweaked for this year with two waist-level hand-warmer pockets making it a little more versatile than it's harness-friendly predecessor. Good news for high altitude trekkers taking in the night sky from outside the tea house we reckon. There's also a new two-way main zip to allow for easier use with a climbing harness."
OutdoorsMagic Review

"I would like to thank all the great people at PHD who make this great jacket. Earlier this year I bought this jacket and used it last month in Nepal for an expedition. I reached the summit of Mera Peak 6461 meters and was comfortably warm with this jacket. Thanks again for the great work."
Denis Put

"The last night camped on the glacier at 4800m was one of the coldest I’ve experienced, -15 C inside the tent, and the booties and Rondoy Jacket were invaluable being worn inside my sleeping bag and helping me have a good night's rest"
John Cameron, Rowaling Valley, Nepal

Comment below relates to the standard Rondoy jacket, which is 120g heavier

"The jackets were incredibly warm and light, equally suited to ensure we were warm when climbing and even when static, melting snow, in the advance camps."
Jonathan Phillips, Imperial College, Obra Valley Expedition (GARHWAL HIMALAYA, INDIA).

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