Kelty Cosmic Synthetic Fill 0 Degree Backpacking Sleeping Bag, Regular – Compression Straps, Stuff Sack Included
Best for
Best 0°F synthetic
Amazon rating
Amazon aggregate, one input among many in the Verdict Score
Based on 3 trusted sources
Current price
$127.96
Updated May 18, 2026 · 1 min read
Sources behind this verdict
10 reviewers weighted by source trust
The consensus
What reviewers found
Synthesized across the trust-weighted source mix below.
Across the reviewers we read, the Kelty Cosmic Synthetic 0°F draws a split verdict. The high-trust verdict at outdoorgearlab.com is blunt — they call it the heaviest, least weather-resistant bag in their winter review and note that while it was once a bargain leader, it no longer leads. Community feedback from r/Ultralight and r/CampingGear echoes the bulk concern, with multiple commenters recommending the Cosmic line for car camping but not backpacking.
What reviewers liked
- Synthetic fill retains warmth better than down when damp — useful for wet winter conditions
- Recycled fabric and PFAS-free DWR are real sustainability features highlighted in retailer listings
- Affordable entry into 0°F territory compared to premium down bags
- Roomier 'updated' mummy fit gets praise from side-sleeping retailer reviewers
Where it falls short
- outdoorgearlab.com explicitly calls it the heaviest and least weather-resistant bag in their winter review
- r/Ultralight and r/CampingGear consensus is that the Cosmic line is car-camping-only weight
- No high-trust evidence the 0°F rating holds for cold sleepers — community guidance is to layer aggressively
- Compression and packed size lag behind down competitors at similar price
Across the reviewers we read, the Kelty Cosmic Synthetic 0°F draws a split verdict. The high-trust verdict at outdoorgearlab.com is blunt — they call it the heaviest, least weather-resistant bag in their winter review and note that while it was once a bargain leader, it no longer leads. Community feedback from r/Ultralight and r/CampingGear echoes the bulk concern, with multiple commenters recommending the Cosmic line for car camping but not backpacking. Verified-purchase reviewers on Amazon are more positive (4.5 stars across about 200 reviews), focusing on warmth, the recycled fabrics, and the PFAS-free DWR treatment.
Where this bag actually fits, per the synthesis, is as an affordable synthetic 0°F bag for car camping or short cold-weather trips where weight doesn't matter and dry-down resistance is a plus. r/CampingGear users who own the Cosmic line specifically prefer the 20°F version with a liner over stepping up to the 0°F, suggesting the 0°F variant is overbuilt for most three-season use. If your goal is true winter use and you don't want to pay for premium down, mainstream reviewers point you toward fully synthetic bags from other brands or accept that you're carrying a heavy bag.
- nylon
- Imported
- 0 Degree Temp Rating, Long Size
- Fits sleepers up to 6ft 6in, fill weight 60oz, total weight 4lbs 11oz, stuff size (non-compressed) 17x11 inches.
- Packability
- Integrated compression stuff sack, coupled with the premium packability of the synthetic fill allow the Cosmic synthetic to reach minimalist standards of backpacking gear. Trail weight varies by temp rating, from 2lbs 6oz to 4lbs 11oz.
- Insulation
- Cirroloft synthetic insulation provides reliable warmth in cold and damp conditions, maintains loft for even coverage with no cold spots. Temperature ratings from 0 degrees to 40 degrees, to ensure your time on the trail is comfortable.
- Tailored Fit
- Natural fit spacious footbox gives more room to wiggle your toes, and length options range to fit sleepers 5’8” to 6’6”. A handy stash pocket on the exterior of the bag for your overnight goodies and essentials in the tent.
- Kelty Craftsmanship
- Kelty is synonymous with quality in the outdoor community. Kelty gear is built for play, and built to last. The Cosmic Synthetic bag is ready to be put through the ringer on the trail, campground, and everywhere in between.
But it is very heavy (mine is 52 oz.) and takes up a lot of space in your pack. I would recommend it for car camping but not anything for ...
It's roomy and comfortable for side sleeping. The two-way zipper is great for ventilation. Packs up pretty small without a compression sack, at ...
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“Kelty Cosmic Synthetic Sleeping Bag Series Review” · YouTube
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