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UL or YF? Two answers, one standard.
Every Feathered Friends three-season sleeping bag uses 100% RDS-certified down and is handcrafted in Seattle. The choice between UL and YF comes down to materials and weight, premium ultralight or durable everyday, at meaningfully different price points.
Premium · Most Popular
UL Series
The lightest, warmest, most premium sleeping bags we make.
Down
950+ fill power goose down
Shell
Pertex® Quantum Pro® · 7 + 30D ripstop
Weight
~3 oz lighter than YF equivalents
Pack size
Smaller stuff sack at the same warmth
Durability
Suprisingly durable, but treat it with care
Best for
Gram-counters, thru-hikers, alpine climbers, fast-and-light missions, and anyone for whom every ounce matters.
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YF Series
Premium quality and durability at a lower price point. Our Penguin, Condor, and Puffin sleeping bags are YF exclusives
Down
900+ fill power goose or Ultrasonic Muscovy
Shell
Pertex® YFuse® · 20D weave
Weight
~3 oz heavier than UL equivalents
Pack size
Slightly larger; still compresses well
Durability
A bit beefier than the lighter UL fabrics
Best for
Most weekend backpackers, car campers, and anyone wanting premium quality at a meaningfully lower price point.
Shop YF Series
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Side by side
The differences at a glance
| UL Series | YF Series | |
|---|---|---|
| Fill power | 950+ goose down | 900+ goose or Ultrasonic Muscovy |
| Shell fabric | Pertex® Quantum Pro® (7 + 30D) | Pertex® YFuse® (20D) |
| Shell weight | 25 g/m² (lighter) | 36.5 g/m² (more durable) |
| Lining | Recycled nylon + Pertex® Diamond Fuse footbox | NetPlus® recycled-net nylon |
| Bag weight (20°F equiv.) | ~3 oz lighter | ~3 oz heavier |
| Sustainability story | Recycled nylon · PFAS-free DWR · RDS down | GRS-certified · Bluesign® · NetPlus® lining · RDS down |
| Best for | Thru-hikers, backpacking, ultralight missions, gram counters | Backpacking, camping, durability-first buyers |
Still on the fence? Our Seattle staff helps people through this exact decision every day. It's a 5-minute conversation that saves you a returned bag.
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The Gold Standard in Down Sleeping Bags
At Feathered Friends, we believe you shouldn't have to choose between a light pack and a good night's sleep. Our three-season bags Ultralight UL Series are filled with premium 950+ fill power goose down, providing an industry-leading warmth-to-weight ratio. Our YF-Series brings buttery smooth fabrics and your choice of 900+ fill power goose down or Muscovy down. Every bag is handcrafted in our Seattle workshop, ensuring the highest standards of quality and ethical sourcing.
Sleeping Bag FAQs
Everybody sleeps very differently. We typically recommend choosing a sleeping bag rated 10ºF below the lowest temperature you expect to encounter.
If you typically sleep colder, we recommend going even lower, perhaps closer to 20ºF colder than expected temperatures.
For more information on choosing a sleeping bag, check out our guide here
Our UL-series sleeping bags get upgraded with a quieter, water-resistant Pertex® Quantum Pro® shell fabric free of PFAS, as well as the introduction of Pertex® Diamond Fuse lining fabric in the footbox for more long-term abrasion resistance.
Most of our three-season sleeping bags are offered with two different materials.
UL: Our highest-end ultralight offering. Made with Pertex® Quantum Pro® water-resistant/breathable fabric and 950+ Fill Power Down. This is for those looking for the absolute best.
YF: YFuse. Made with a buttery smooth Pertex Quantum® YFuse 20 denier mini-ripstop fabric and either 900+ fill power goose down or 900+ Ultrasonic Muscovy duck down. Ideal for those who want a premium down sleeping bag, but at a lower price.
We use 950+ fill power goose down in our UL (ultralight) and Tanager sleeping bags.
900+ fill power goose down is available in all of our ES (winter & expedition) sleeping bags as well as our YF series.
900+ fill power ultrasonic Muscovy down is also available in our YF series of three-season sleeping bags.
Each and every sleeping bag we make is made in Seattle, Washington.
Yes! Most of our bags are designed to be compatible. To zip together, you typically need one Men’s/Unisex bag (Left Zip) and one Women’s bag (Right Zip). Our zippers are standardized #5 YKK, allowing different models to be paired, though we recommend matching the temperature ratings for the best experience.
Men's/Unisex: Regular fits up to 6'0", Long fits up to 6'6".
Women's: Small fits up to 5'3", Medium fits up to 5'9".
Pro Tip: If you are right on the edge (e.g., 6'0"), we recommend the Long to ensure your feet and head don't compress the down at the ends, which can create cold spots.
Never store your down bag in its small compression stuff sack! Long-term compression can damage the down clusters and reduce loft. Every Feathered Friends bag includes a large, breathable cotton storage sack. Keep it in a dry, cool place where it can stay uncompressed.