Feathered Friends Swallow UL 20 Sleeping Bag Review

Feathered Friends Swallow UL Sleeping Bag Review

The Feathered Friends Swallow UL 20 is a 27 oz ultralight mummy sleeping bag that excels during shoulder season conditions in spring and autumn when nighttime temperatures approach or drop below freezing. While I have used premium down quilts in such weather, I now prefer the efficiency and reliability of the fully enclosed Swallow UL down sleeping bag.

Specs at a Glance

  • Temperature Rating: 20*F / -6.67*C (also available in 30*F / -1.1*C)
  • Gender: Unisex
  • Fill Power: 950+ RDS-certified, trackable goose down
  • Size: Regular 6’ 0” / 183 cm, (also available in Long 6’ 6” / 198 cm)
  • Dimensions: 60” / 56” / 38”
  • Average Weight: 27 oz / 766 g (my example weighs 27.4 oz)
  • Fill Weight: 16.7 oz / 476 g
  • Packed Size: 9L
  • Collar: Passive collar
  • Baffles: Continuous
  • Outer Shell Fabric: Pertex Endurance UL (10 denier)
  • Lining Fabric: Flite 15 denier ripstop nylon
  • Zipper: Left side #5 YKK two-way, separating zipper with draft tube
  • For complete specs, visited FeatheredFriends.com

A Former Cold Weather Quilt Sufferer

I’m not bashing backcountry quilts. They still have a place in my summer pack, and some users implement them with great success in colder temperatures. But, after years of experimenting with 10-20*F rated quilts from Katabatic Gear, Enlightened Equipment, and Zpacks, I always struggled to stay warm in their quilts when temperatures dropped below freezing.

The hood is deep enough to use an inflatable backpacking pillow.
The hood is deep enough to use with an inflatable backpacking pillow.

In my experience, I found the modularity of quilts in lower temperatures to be more of a nuance than an advantage. Piecing together a layered system meant added weight and complexity while supplementing with extra layers reduced the lifespan and effectiveness of my down jackets. As a restless sleeper, I couldn’t eliminate draft issues, even utilizing an extra-wide quilt with a well-engineered pad attachment system.

My down jacket hood and beanie also didn’t offer enough head warmth so I added a down balaclava to my kit. At that point, the weight of the system crept up into mummy bag territory, and I started to rethink my cold weather strategy.

By utilizing an enclosed mummy bag for backpacking in colder temperatures, my bag time at night offered greater rest and recovery. The negligible, if any, increase in total pack weight didn’t slow me down. It allowed me a higher quality of sleep while increasing my physical ability, injury resistance, and mental stamina. I still use and enjoy quilts for warmer weather use, but believe the Feathered Friends Swallow UL 20 is a practical and effective shoulder season choice while still adhering to ultralight backpacking principles.

The seams on the Swallow UL 20 are straight and tight with excellent craftsmanship.
The seams on the Swallow UL 20 are straight and tight with excellent craftsmanship.


Feathered Friends prides itself in quality manufacturing and impeccable craftsmanship. The stitching on the Swallow UL 20 is superb, straight, and tight. I now own two Feathered Friends sleeping bags, the Swallow UL 20 and the hoodless, zipperless Tanager UL 20. You simply can’t sew anything better. Both are made in Seattle, USA with imported materials and have a sound warranty.

Fill Power

Feathered Friends uses the highest quality, RDS-certified, trackable goose down in the world and the regular length Swallow UL 20 is stuffed with 16.7 ounces of 950+ fill power down. Feathered Friends states their down is just that, high-quality down clusters free of feathers and quills. My particular example is IDFL tested and verified 990 fill power down, with 94.8% down cluster. That’s not a typo: 990 fill power goose down!

The Swallow UL 20 is designed with continuous baffles.
The Swallow UL 20 is designed with continuous baffles.

Continuous Baffles

The Swallow UL 20 is designed with continuous baffles. Continuous baffles allow the end-user to shift down around the bag as needed. This is not something I’ve really exploited in the field to the extent of minutely adjusting the warmth of the bag. I do have a nightly routine where I take my bag out of my pack and shake it out to distribute the down. This allows it to loft faster and mitigates down clumping over multiple nights of use. If pushing the temperature limits of the bag I focus a bit more on shaking down to the top and sides of the bag. Moving down around the continuous baffles works best when the bag is fully lofted and dry.

Mummy Hood

The hood on the Swallow UL 20 is not the largest or warmest hood on the market in order to keep the bag weight down. It is, however, adequately sized and warm for its purpose. It is also deep enough that I can put an inflatable pillow into the hood and still retain warmth around my head. Having a dedicated hood to capture a pillow is a major increase in comfort and keeps it from sliding around on a pad.

In colder temperatures, I put my pillow under the hood of my bag and cinch the hood up tight around my head. The hood has a satisfyingly smooth cinch which can be loosened up in warmer temps or cinched down to capture greater warmth.

The 3D contoured hood is comfortable and warm.
The 3D contoured hood is comfortable and warm.

Passive Collar

The Swallow UL 20 does not have a substantial draft collar as found in colder weather, winter, and expedition bags. It has a passive collar, which provides a bit more down around the neck to trap warmth. For the given temperature rating, I have found it to be adequate. This is another design characteristic that keeps the Swallow UL 20 low weight.


I typically avoid zippers on backpacking equipment. With that said, I don’t find quality mummy bag zippers to be problematic. They don’t get dirty or salty like that on a tent. The Swallow UL 20 uses a two-way separating #5 YKK zipper with locking sliders. It operates smoothly and incorporates a generous draft tube to mitigate cold spots.

The zipper sports a generous draft tube to seal out cold air.
The zipper sports a generous draft tube to seal out cold air.

For longevity and to reduce headaches on trail, I’m always mindful when operating all zippers on gear, and in the case of the Swallow UL 20, I have zero complaints on how the zipper operates. No snags, no sticking, no issues. The zipper incorporates a fabric guard which greatly mitigates snags. Truth be told, one of my favorite characteristics of the mummy bag is the zipper itself which renders the ability to seal in precious warmth at night over a quilt.

Trapezoidal Footbox

The trapezoidal design is ergonomic and warm. I am generally a size 11.5 (45.5 EU) men’s trail runner, and the footbox of the Swallow UL 20 is spacious enough to perform foot yoga in. In poorly designed footboxes, lack of space or compressed down is quickly apparent by feeling restricted around the feet and ankles or experiencing cold spots. The footbox design on the Swallow UL 20 allows my ankles and feet to rest naturally and not compress the surrounding down.

I’ve experienced cold feet with other quilts and bags. For many years, I believed it was a physiological problem and incorporated supplemental insulation such as possum and goose down socks. Since switching to the Swallow UL 20, my cold feet issue has largely disappeared.


The Swallow UL 20 is certainly on the warmer side and overkill for hot summer nights, but it can be unzipped and used wide open to drape over oneself to mitigate overheating. The bag really excels in lower temperatures, but it’s appropriate for a variety of three-season conditions as a do-it-all option.

I switch to a stripped-down, summer weight quilt in consistently warmer temperatures (40*F and greater at night) to further reduce pack weight and volume. But if I could only have one option to cover my spring, summer, and fall backpacking trips, I’d make it the Swallow UL 20.

The trapezoidal footbox allows feet to rest naturally with minimal down compression.
The trapezoidal footbox allows feet to rest naturally with minimal down compression.


The Swallow UL 20 is Feathered Friend’s unisex, medium-width mummy bag which falls between the Hummingbird (slimmer) and Swift (widest) models. At 5’ 8” and 155 lbs, I am very comfortable inside the Swallow and do not find it confining or overly voluminous. I have ample amount of space to roll over or layer up with a down jacket without compromising loft. I toss and turn, and do not get tangled up in the Swallow UL 20. The 6’ 0” length is appropriate for me and I can stretch out in the bag at night.


My Swallow UL 20 weighs 27.4 ounces. This is an impressive weight for a feature-rich, accurately rated mummy bag. The efficient design and ultralight materials keep the weight down without sacrificing comfort or warmth.

In general, backcountry quilts are considered the lighter alternative to traditional mummy bags. In colder temperatures, I find this not entirely true. I need an extra-wide quilt, pad attachment system, down balaclava, and supplemental layers to achieve the same comfort experienced with the enclosed Swallow UL 20 bag. Weight differences between the two systems become negligible, and the draft-free, no-fuss warmth and comfort of a mummy bag performs better in lower nighttime temperatures.

The two-way zipper allows venting or kicking your feet out.
The two-way zipper allows venting or kicking your feet out.

Packed Size

The Swallow UL 20 is very compressible due to the high fill power and ultralight materials selection. For those searching out a dimensionally comfortable, 20*F, zippered mummy bag with a hood, it packs as small as one could ask for at the given temperature rating. I have no problems stuffing this bag into a 40L backpack with an accompanying three-season, ultralight loadout. The difference in packability with a comparable quilt is negligible.

Pertex Endurance Shell Fabric

The Swallow UL has 10 denier, 0.94 oz / yd2 water-resistant breathable ripstop shell. Its modern tech, super light shell fabric may feel anemic for first-time users, but when treated with proper care, it will go the distance. I’ve spent over 500 nights in another manufacturer’s 10d Pertex quilt, and the only imperfection is a slight color fade from multiple wash cycles.

The 10d fabric breathes well and dries fast. Tenacious tape provides a clean and reliable field repair for less than fortunate events. The DWR shouldn’t be used as a primary defense against moisture, and precautions must be taken to ensure the untreated, yet lofty down doesn’t become susceptible to excessive wetness.

Flite 15 Inner Fabric

The inner Flite 15 fabric of the Swallow UL 20 is soft, breathable, and dries quickly. I keep it clean by wearing dedicated sleep layers the majority of the time. If your skin or clothes are damp, or the humidity is high, most synthetic fabrics will feel a touch clammy or sticky.

If the Feathered Friends Swallow UL 20 were a painting, it would belong in a museum.
If the Feathered Friends Swallow UL 20 were a painting, it would belong in a museum.


The Feathered Friends Swallow UL 20 is a premium mummy sleeping bag that is lightweight enough to go head to head with backpacking quilts in terms of warms and comfort in freezing temperatures. If you struggle to stay warm with a quilt in cool spring or autumn weather. I’d encourage you to reconsider the use of a sleeping bag like the Feathered Friends Swallow UL 20.

While the Swallow UL 20 checks all the boxes in terms of size, specifications, features, and materials, you can’t customize a Feathered Friends sleeping bag the way you can with a quilt from a cottage vendor. That’s just a compromise you have to make when buying an off-the-shelf product. Still, while it might not be the most luxurious 20*F mummy bag available, the Swallow UL 20, might just be the most efficient from a performance standpoint.

Since purchasing my Swallow UL 20, I’ve also purchased a Feathered Friends Tanager 20 Hoodless Sleeping Bag and the midweight Feathered Friends EOS down jacket which are also highly functional and beautifully made. If I ever need to purchase another sleeping bag, down jacket, or accessory, Feathered Friends products will definitely be on my shortlist.

Disclosure: The author owns this product.

The Feathered Friends Swallow UL 20 is only available from Featured Friends

Editor’s note: If you’re thinking about buying gear that we’ve reviewed on SectionHiker.com, you can help support us in the process. Just click on any of the seller links above, and if you make a purchase, we may (but not always) receive a small percentage of the transaction. The cost of the product is the same to you but this helps us continue to test and write unsponsored and independent gear reviews, beginner FAQs, and free hiking guides. Thanks and we appreciate your support!

About the author

Tim Wentzell is a long-distance backpacker, dedicated peak bagger, and second-rate climber. His hikes have taken him up and down the east coast in all four seasons. He has completed thru-hikes of the Appalachian Trail, Vermont Long Trail, and Cohos Trail. Tim spends his time backpacking the White Mountains (NH), base camping around a campfire, and planning the next summit push while living in the Northeast Appalachians. Driven by efficiency, his engineering background keeps him studying the intricacies of equipment and how it integrates us with the backcountry. Tim began documenting his experiences in an effort to capture a greater understanding of a life outdoors. Follow him at https://www.2milesperhour.com

Leave a Reply

Your email address will not be published.