Alpinist Center Zip Mummy - Four Season

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The Alpinist is Nunatak's center zip mummy bag.


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In our line-up for more than 20 years, the Alpinist is based on a design pioneered by Yvon Chouinard in the early seventies. The original is allegedly still used by Chouinard, as mentioned in the 2017 Patagonia catalog.

The unique center zip location is perfect for side sleepers and back sleepers alike. It also gives you full use of both arms while still having head and back snug in the sleeping bag, a must when performing sitting camp tasks in less than ideal conditions.

When side sleeping the zipper typically ends up slightly in front, down from the shoulder a bit. Whether it is open for venting or snugged up, this is an ideal location. From here the zipper is conveniently controlled without contortions, and the dreaded back side cold spot from traditional zipper placement on the side hem, is completely eliminated. In fact, side sleeping is probably where the center zip placement is at its best.

The Alpinist is built with a differential cut, a feature that greatly increases the efficiency of a given fill volume; and the zipper is backed by a double set of draft tubes. Internal shoulder level draft collar is standard.

Take note that the Alpinist performs best close to its comfort rating, as venting the lower portion is difficult on warmer nights. For general backpacking the versatility of the hoodless/zippered 3D Quilt with is superior.


Two levels of insulation. Conservatively defined as 15°F or 5°F. The loft is a minimum of 2.75" and 3.25".  Fill volumes for either level are detailed in the charts below, and offer further insight into whether these quilts will meet your needs. 

Advanced baffle layout. Together with our carefully calculated fill volumes, the tapered and individually optimized baffles help to eliminate migrating down and cold spots. Along with loft, these are crucial design components for a cold weather bag.

Internal shoulder level draft collar. Down filled on 15°F and 5°F versions - unfilled on 35°F and 25°F bags.

Differential cut. The outside of the bag is built with a proportionally larger girth and length. This keeps the insulation fully lofted even when attacked by a restless sleeper.

Enhanced moisture protection in areas of exposure. Optional waterproof/breathable fabrics protect the upper bag where moist exhalations can wet out the insulation; as well as the foot section, an area often rubbing with damp shelter walls. This performance fabric adds little additional weight to a finished Alpinist.

Goose down. We use only high quality 900 fill power goose down, in plain untreated or Hyper-Dry to resist loft-killing moisture. Our batches are certified ethically sourced/harvested and can be tracked upon request.

Optional lining of extra durable fabric in the fully enclosed footbox. This area typically sees the most wear, whether from calloused feet or the storing and drying of footwear. Substituting the standard liner for a 20D material gives this area an edge in long term durability. Expect a minor weight increase.

Dual draft tubes along the zipper

Adjustable cord around the snug hood opening.

Two way #5 zipper.

NOTE: These highly specialized bags have a narrow comfort range due to the center zip efficiency and lack of venting options for the foot end:

15°F : 10°F to 20°F

5°F : 0°F to 10°F

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Alpinist Center Zip Mummy - Four Season

Alpinist Center Zip Mummy - Four Season

Temporarily closed, see top banner

The Alpinist is Nunatak's center zip mummy bag.


Product Options
15°F / -10°C
5°F / -15°C
Inside Length
62" - Extra Short
66" - Short
70" - Medium
74" - Long
78" - Extra Long
Shoulder Width
54" inside circumference. Small frames, skinny people
60" inside circumference. Fits most.
66" inside circumference. Very roomy.
Footbox Size
40" circumference foot end
44" circumference foot end
Differential Cut
Yes. Please!
Shell Material

Moroccan Blue Ripstop 10d - Lightest, most breathable
Grey Ripstop 10d - Lightest, most breathable
Purple Ripstop 10d - Lightest, most breathable
Forest Green Ripstop 10d - Lightest, most breathable
Dark Olive Ripstop 10d - Lightest, most breathable
Brilliant Blue Ripstop 15d - More durable, breathable
Black Ripstop 15d - More durable, breathable
Purple Ripstop 15d - More durable, breathable
Dark Olive 15d - More durable, breathable
Multicam 40d - Durable, water repellent - Balances well with 20d liner
Liner Material Options
Black 10d taffeta - Lightest, most breathable
Black 20d taffeta - Durable, soft and comfortable but about an ounce heavier!
10d black taffeta in torso section, more durable 20d taffeta in foot section
Down Type

Allied Expedry is a moisture resistant goose down treated with a chemical free, safe compound. Expedry helps reduce drying times while minimizing performance issues in wet weather. The treatment is long lasting and effective.

Untreated 900fp goose down only available on request.

900 Fill Power Goose Down, Expedry, RDS Certified
Down Overfill

Adding overfill can prolong the life of the down, help maintain loft during moist conditions, boost the temperature rating by a small amount and keep the down volume from shifting. For most quilts/bags the overfill amount ranges from 45-65 grams of extra down

No Thanks
Overfill in foot section
Overfill in torso section
Overfill evenly throughout
Zipper Length
38" - #5 - Two-way, inside/outside pull
Your Measurements
Shoe Size 
Stuff Sack
Yes, please include a stuff sack
No stuff sack