Kelty
Kelty Cosmic Ultra 0
Best budget friendly down bag for cold weather backpackers.
Designed for cold-weather excursions, this mummy-style sleeping bag offers exceptional thermal efficiency and reliability in freezing conditions. It utilizes high-loft, moisture-resistant down insulation that maintains warmth even in damp environments. The advanced trapezoidal baffle construction traps heat effectively, while the spacious, natural-fit footbox allows for comfortable movement throughout the night. Crafted with a durable, lightweight nylon shell and a soft liner, it features an anti-snag zipper for effortless entry and exit. This versatile gear balances weight and performance, making it an essential companion for backpackers seeking reliable comfort and protection during demanding three-season adventures.
$369.95
More Cosmic Options
Cosmic 20
$159.95
Cosmic Down 20
$189.95
Cosmic Synthetic 0 Degree
$139.95
Cosmic
$314.95
Cosmic 20 Sleeping Bag (Long)
$109.95
Cosmic Synthetic 20 Degree
$119.95
Cosmic 40
$119.95
Cosmic Synthetic 20
$109.95
Cosmic Ultra 20 Degree
$269.95
Cosmic 20 Degree Sleeping Bag
$169.99
Cosmic 20 Sleeping Bag
$118.22
Cosmic Ultra 0°F Sleeping Bag
$219.95
Cosmic Ultra 800 DriDown Sleeping Bag
$184.48
Cosmic 0 Synthetic Sleeping Bag
$129.95
Cosmic 20 Sleeping Bag
$118.22
Cosmic Ultra 0°F
$245.97
Kelty Cosmic 20
$169.99
Kelty Cosmic Synthetic 0 Degree Sleeping Bag
$166.00
Kelty Cosmic Down 20
$189.95
Cosmic Synthetic 40 Degree
$99.95
Cosmic Synthetic 20
$109.95
Owner Satisfaction
4.5
/ 5
Category Rank
1010
/ 2020
#1010 in Sleeping Bags
Price vs Category Average
+30%
Above average
Temperature Rating
0
/ °F
Who it's for
- Budget-conscious winter campers seeking reliable warmth without the premium price
- Backpackers facing humid or snowy environments who need resilient insulation
- Restless sleepers who need consistent heat retention while moving around
Who should skip it
- Ultralight hikers with limited internal pack space for winter gear
- Ounce-counting trekkers prioritizing the lightest possible base weight
- Broad-shouldered campers or side-sleepers who feel claustrophobic in tight bags
Key Specs
Temperature Rating
0°F
Bag Shape
Mummy
Insulation Type
Down
Fill Power
800 cubic inches per ounce
Weight
4.17 lbs
Shell Material
Nylon
Lining Material
Nylon
Zipper Location
Side
Know before you buy
While it is rated for 0°F, the ISO Comfort rating is 18°F, which is the temperature at which an average sleeper will feel comfortable. The 0°F rating is a survival limit, so plan on using this bag for late-fall or winter camping where temperatures hover around 15°F to 20°F for the best experience.
DriDown is treated to be moisture-resistant, meaning it retains its loft and warmth much better than untreated down if it gets damp. However, it is not waterproof, so you should still use a waterproof stuff sack or pack liner to keep the bag dry during transit.
The Cosmic Ultra 0 features a natural-fit footbox designed to give your feet more room to move, which helps reduce that claustrophobic feeling common in traditional mummy bags. While it is still a performance-oriented fit, it is engineered to balance thermal efficiency with enough space for comfortable movement.
No, the bag is equipped with an anti-snag zipper system specifically designed to prevent the fabric from catching in the slider. This makes getting in and out of the bag much easier, especially in the dark or when you are in a hurry.
The bag weighs 4.17 lbs, which is reasonable for a 0°F winter-rated bag but on the heavier side for ultralight summer backpacking. It is best suited for winter camping, car camping, or shorter backpacking trips where you prioritize warmth over shaving every ounce of weight.
This construction method helps keep the down insulation evenly distributed and prevents cold spots from forming. By maintaining consistent loft throughout the bag, it ensures you stay warmer for longer without needing to constantly adjust the insulation.
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$370