Arc UL - 30°/40°F

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The Arc UL quilts are designed for optimal efficiency in the environments met by long distance hikers.Custom features including sizing and weight saving options. 

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Custom item. Multi week lead time.

Appropriate use

This Arc UL is designed to balance the lowest possible weight and bulk with the level of comfort needed in the western US mountains during the height of the summer hiking season. 

The two temperature ratings on the menu are realistically defined as either 40° or 30°FThe loft is a minimum of 1.25" or 2.0".  

The 30° Arc UL is warm enough to serve as a general purpose quilt for an experienced backpacker in a variety of environments.

The 40° version is the 'go light and fast' choice with obvious compromises in cold weather ability.

Fill volumes are detailed in the charts, and offer further insight into whether these quilts will meet your needs.


The length is in 4" increments defined by measurements plus X-Small to X-Long descriptors. Using this system you can choose how far up the quilt reaches when on your back. In open mode reaching just the chin level is the absolute shortest anyone should go, and then only on quilts for the warmer seasons. Reaching the user's forehead is the best compromise of low weight - efficient coverage. As always, it is prudent to size up if in doubt. If just a little too short one tends to compress the foot area insulation to the detriment of cold toes.

The shoulder and foot area widths can be customized for individual needs and sizing. Newcomers to backcountry quilts can experiment with a blanket before committing to a sizing setup. 

Foot End Design

The Arc UL quilts are offered in two foot box configurations, also in the menu below. The traditional Arc design is a permanently closed section finished with a round bottom piece sewn in place. A design common with high-end mummy bags.

The Vector foot end allow the user to switch from closed to blanket style open foot area in a few simple steps. This option, while very adaptable to changing conditions, lack a in thermal efficiency compared to the regular Arc. It also adds some weight, for those who count every gram. A page with a few pics detailing the foot box options is here.

Shell Material Choices

Immediate apologies for the complexity of the following! 

We offer the discerning user an option to fine tune the performance of the Arc UL via a series of technical shell materials.

Basically there’s three distinct categories:

1: Classic breathable shell. 

These ultralight choices create a comfortable sleep environment at the lowest weight. They will, however, wet out and transfer moisture to the down if exposed to dew, mist and damp tents. On the other hand, the superior breathability allows them to dry quickly in the sun. Ideal for moderately dry weather, desert hikes and anyone with a traditional double walled tent.

2: Robic ultralight waterproof and breathable shell.  

With this as your outer material there’s minimal concern about external moisture migrating to the down. Also, the lesser breathability boosts the temperature rating a small amount.

The choice for wet environments, ‘cowboy camping’ and for users of flat tarps wanting to eliminate the bivy bag. The Robic has a very light denier count, and as such adds under 5% to the total weight over the Classic option.

3: A combination of Classic and Robic shells. 

With Robic only covering the outer foot section and top draft collar you can protect the down where it matters the most, while leaving the large mid section fully breathable. For use in the modern single wall tent where rampant condensation often collides with the lower end of sleeping bags. Also, the draft collar is protected from moist exhalations. A very versatile setup.

Look closely at the configuration table below, in order to select precisely what suits your use.

Liner Material Choices

The worst long term wear on quilt fabrics is the inside liner material. If you want to break with true UltraLight traditions, and risk adding up to 2 ounces (!!) of weight, the Arc UL can be upgraded to our soft, durable 20d Taffeta black liner, specifically developed for sleeping bags. 


Besides the custom sourced shell and liner materials, we also consider shock cords, buckles, snaps and other notions as specific targets for UL optimization, further shaving grams. 

What's in the box?

The quilt, a set of quilt straps, a silnylon stuffsack and a large breathable storage sack.

We also have additional articles with helpful pointers on selection and design:

Choosing the right Quilt

Quilt Straps and Cords

Designing with Down

Go to the bottom of this page for the full Arc UL Configuration Menu.


Length and width choices affect fill weight by roughly ½ to 1 ½ oz, depending on temperature rating.

After saving your customized product, remember to add it to your cart.



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Arc UL - 30°/40°F

Arc UL - 30°/40°F

The Arc UL quilts are designed for optimal efficiency in the environments met by long distance hikers.Custom features including sizing and weight saving options. 

Product Options
Temperature Rating
The rating reflects the lowest temperature during which a well conditioned hiker can expect to remain comfortable throughout a full night. Adequate shelter and ground pad must be used.
40°F / 5°C
30°F / 0°C. Includes differential cut
Inside Length
To determine the correct length please refer to the measurements in the chart.
Shoulder Width
54" is a good standard for regular sized folks who doesn't toss around too much. For winter bags go one size up.
Foot End Style
The Arc is the well known enclosed footbox sewn with a rounded bottom piece.
The Vector gives you the option of opening up the quilt's foot area to a blanket style appearance. This comes with a compromise in thermal efficiency and a weight increase.
ARC. Permanently Enclosed Foot Box
VECTOR. Convertible - Blanket to Enclosed
Footbox Size
40" is the male size 10-11 shoe standard. Adjust accordingly.
Shell Material Options

These are the Classic breathable ultralight shell options, typically listed from lightest to most durable. 

Please go to the Fabric Page for help choosing the shell material.

Waterproof/Breathable Shell Options

The top four in this selection applies a 7d waterproof/breathable shell fabric to the foot section, plus the top near the head opening. The large vertical baffled middle section remain with the material/color chosen in the previous field . Select colors to match - or not! The second choice, represented by 'Full Coverage', will completely replace all other shell choices with a full coverage of the same waterproof/breathable 7d ultralight shell.

Liner Material Options
Choose between lightest - the 10d - or long lasting comfort at the penalty of several ounces extra weight: the 20d
Down Type
Choosing Hyper-Dry moisture resistant down will help combat the effects of perspiration, misting tents and damp air. Nunatak products made with Hyper-Dry down will have a slight increase in bulk over those made with regular down. A 5% increase in fill weight also occur.
900 Fill Power Goose Down, RDS Certified
900 Fill Power Goose Down, Hyper-Dry, RDS Certified
Edge Tension Control

This design involves two user adjustable shock cords running lengthwise along the left and right quilt edges. On cold nights tension the cords to shorten the edges and draw them under you; during milder conditions completely slacken the cords to have the blanket throw feel. Go here for more info

No Thanks
Yes, Include Edge Tension Control
Strap package

Straps snug the quilt around you and/or the sleeping pad. Go here for more info

Gamut Climashield Over-quilt Compatability
This mod makes a future over-quilt application as effective as possible. It adds snap buttons in the places needed, plus stores a record of your product's finished measurements and attachment points.
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. Expect a weight increase ranging from one to six ounces depending on the product, the size and the rating.
Your Measurements
Optional: Fill in the blanks to ensure getting the best fit. No changes will be made to your size selections without approval
Shoe Size