Kelty Cosmic Synthetic Fill 40 Degree Backpacking Sleeping Bag with Compression Straps, Compact and Lightweight, 2022
Best for
Best 40-50°F bag
Amazon rating
Amazon aggregate, one input among many in the Verdict Score
Current price
$99.95
Updated Jun 27, 2026 · 1 min read
The consensus
What reviewers found
Synthesized across the trust-weighted source mix below.
The Kelty Cosmic Synthetic 40 lands a 4.6 average across the verified-purchase reviews available, though on a relatively small base of 94 ratings. Its 40°F rating, synthetic fill, and included compression straps position it squarely as a warm-weather and shoulder-season backpacking bag, and the synthetic insulation makes it more forgiving in damp conditions than the down Cosmic. Buyers note the compact, lightweight packing the compression system enables.
What reviewers liked
- 40°F synthetic rating is well matched to summer and shoulder-season use
- Compression straps aid compact packing
- Recognized brand with a 4.6 verified-purchase average
Where it falls short
- Low review volume (94) limits confidence in the consensus
- Synthetic fill packs bulkier and heavier than down
- No expert or community signals available to corroborate the rating
Embed our score
Sell this product? Show off the rank.
Free badge for the brand, retailer, or anyone covering this product. Copy the snippet and paste it anywhere HTML works. Updates automatically when the ranking changes.
Includes a credit link back to this page. No tracking; no JavaScript.
The Kelty Cosmic Synthetic 40 lands a 4.6 average across the verified-purchase reviews available, though on a relatively small base of 94 ratings. Its 40°F rating, synthetic fill, and included compression straps position it squarely as a warm-weather and shoulder-season backpacking bag, and the synthetic insulation makes it more forgiving in damp conditions than the down Cosmic. Buyers note the compact, lightweight packing the compression system enables.
As with the rest of this pool, no independent lab data, verified-publisher measurements, or specialist-community threads were supplied for this specific listing, so the read is based on Amazon retailer signal alone. The rating is strong but the review count is modest, which limits how much confidence the consensus can carry. Synthetic fill also means it will pack slightly bulkier and weigh a touch more than a comparable down bag.
- 20D nylon
- Imported
- 40 Degree Temp Rating, Regular Size
- Fits sleepers up to 6ft, fill weight 24oz, total weight 2lbs 6oz, stuff size (non-compressed) 15x8 inches. Color: Duffel Bag Green/Smoke
- 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.
If the consensus convinced you
Check current price on Amazon
Pricing and availability change frequently. Tap through to confirm before buying.