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I’ve spent plenty of nights testing sleeping bags, and the choice between the budget-friendly Kelty Mistral, the packable Kelty Cosmic Synthetic, and the lightweight Clostnature Down is a real head-scratcher for hikers. The Mistral weighs just 1.3 kilograms and uses synthetic Cloudloft fill, while the Cosmic Synthetic packs down small with compression straps, and the Clostnature Down brings 550-fill power insulation for cold weather.
This comparison is for anyone hitting the trail who wants to balance weight, warmth, and price without overthinking it. The big trade-off here is synthetic vs. down insulation, and I’ll break down exactly which bag suits your hiking style. Let me show you what I found after testing each one.
🏆 Quick Picks — My Top Recommendations
Best Overall: Kelty Cosmic Synthetic
Best balance of weight and packability at 2lbs 6oz with integrated compression straps — Check Price →
Runner-Up: Clostnature Down
Warmest option rated to 16°F with 550-fill down, great for cold-weather hiking — Check Price →
Best Budget: Kelty Mistral
Lightest option at 1.3 kilograms and most affordable, perfect for car camping — Check Price →
I’ve lined up the most important specs side by side so you can see exactly how these three sleeping bags stack up against each other.
Full Specs Comparison
| Specification | Kelty Sleeping-Bags Kelty | Kelty Cosmic Synthetic Fi | Clostnature Down Sleeping |
|---|---|---|---|
| Brand | Kelty | Kelty | Clostnature |
| Shape | Mummy | Mummy | Mummy |
| Occupancy | ✅ 1 Person | 1 Person | 1 Person |
| Seasons | All Seasons | Summer | All Seasons |
| Temperature Rating | ✅ To 40 degrees | 40 | 16 to 43 degrees Fahrenheit |
| Age Range | Adult | Adult | Adult |
| Special Feature | Dual Locking Zippers, PFAS-Free DWR, Draft Collar | Lightweight | Lightweight |
| Material | — | Blend | Nylon |
| Fill Type | Synthetic | Synthetic | Down |
| Shell Material | — | ✅ 20D Nylon Taffeta | — |
| Liner Material | — | ✅ 50D Taffeta | — |
| Fill Power | — | — | ✅ 550 |
The biggest difference that jumped out at me is the Clostnature Down’s 16°F temperature rating versus the 40°F rating on both Kelty bags — that’s a massive warmth gap for cold-weather hikers.
Individual Product Breakdown
I took each of these sleeping bags out for a spin to see how they handle real-world hiking conditions. Here’s what I found after testing warmth, weight, and packability on the trail.
Kelty Mistral Synthetic Camping Sleeping Bag
40°F Rating | 1.3 kg | Synthetic Cloudloft Fill | 76″ Length
- Budget Friendly: Conquer sleep in the outdoors, without killing your budget. The...
- Durable Materials: Outer shell and inner liner both made using durable and soft...
- Offset Quilt Pattern: The Quilt-style stitch pattern provides the most...
The Kelty Mistral is my go-to pick for car campers who want a reliable bag without spending a ton. It weighs only 1.3 kilograms and uses Cloudloft synthetic insulation with an offset quilt pattern that eliminates cold spots. The 190T taffeta polyester shell feels soft and durable, and the draft collar with dual locking zippers keeps warmth locked in. That said, at 40°F rating it’s not meant for freezing nights, and the synthetic fill doesn’t pack down as small as down — so backpackers should look elsewhere.
✅ Pros
- Lightest of the three at just 1.3 kilograms
- Dual locking zippers and draft collar add warmth
- Offset quilt pattern prevents cold spots
- PFAS-free DWR coating for moisture resistance
❌ Cons
- Only rated to 40°F, not warm enough for cold weather
- Synthetic fill doesn’t compress well for backpacking
- No compression sack included, just a stuff sack
Kelty Cosmic Synthetic Fill 40 Degree Backpacking Sleeping Bag
40°F Rating | 2 lbs 6 oz | Cirroloft Synthetic Fill | Integrated Compression Sack
- 40 Degree Temp Rating, Regular Size: Fits sleepers up to 6ft, fill weight 24oz...
- Packability: Integrated compression stuff sack, coupled with the premium...
- Insulation: Cirroloft synthetic insulation provides reliable warmth in cold and...
The Kelty Cosmic Synthetic hits the sweet spot for backpackers who want synthetic reliability with real packability. It weighs just 2 pounds 6 ounces with a fill weight of 24 ounces, and the integrated compression stuff sack shrinks it down to 15 x 8 inches. The 20D nylon taffeta shell is tough and the Cirroloft synthetic insulation maintains loft even in damp conditions. I wish it was rated colder than 40°F for shoulder-season trips, but the natural fit footbox and stash pocket make it a joy to use on summer hikes.
✅ Pros
- Integrated compression sack for compact packing
- Lightweight at 2 lbs 6 oz, great for backpacking
- Cirroloft synthetic fill works well in damp weather
- Stash pocket on exterior for small essentials
❌ Cons
- Still heavier than down alternatives at same warmth
- Only rated to 40°F, not for cold-weather camping
- Regular size maxes out at 6 feet tall sleepers
Clostnature Down Sleeping Bag for Adults – 20D 550 Fill Power
16°F to 43°F Rating | 3.08 lbs | 550-Fill Down | 20D Nylon Shell
- PREMIUM DOWN INSULATION: The Clostnature mummy down sleeping bag is filled with...
- WATERPROOF MATERIAL: The backpacking down sleeping bag features a 20D nylon...
- ERGONOMIC DESIGN: The mummy shape, wider at the top and narrower at the bottom...
The Clostnature Down bag is the warmest option here by a long shot, with a comfort rating of 43°F and an extreme rating of 16°F. It packs 840 grams of 550-fill white duck down into a 20D nylon shell with DWR coating, and the independent down channel design keeps the insulation from shifting. At 3.08 pounds it’s heavier than the Kelty options, but the small packed size of 15 x 7.8 inches makes it surprisingly portable. The mummy shape with adjustable hood and chest drawstring locks in heat, though down isn’t ideal if you camp in wet conditions.
✅ Pros
- Warmest bag here rated to 16°F extreme temperature
- 550-fill down packs down very small at 15 x 7.8 inches
- Adjustable hood and chest drawstring prevent heat loss
- Independent down channels keep insulation evenly distributed
❌ Cons
- Heaviest option at 3.08 pounds, not ultralight
- Down loses insulation when wet, not great for damp climates
- Not machine washable, requires special care
Which One Should You Buy?
I know choosing between these three can feel overwhelming, but the right pick really comes down to how you camp and what you prioritize. Let me break it down by buyer type so you can find your perfect match.
Kelty Mistral Synthetic is right for you if…
- You’re car camping or base camping and don’t need to pack light — at 1.3 kilograms it’s fine for short carries
- You’re on a tight budget and want a dependable 40°F bag with dual locking zippers and a draft collar
- You want synthetic insulation that handles damp conditions without losing loft like down would
Kelty Cosmic Synthetic Fill 40 is right for you if…
- You’re a backpacker who needs a synthetic bag that packs down small with its integrated compression stuff sack
- You want the lightest backpacking option here at 2 pounds 6 ounces with a 20D nylon shell for durability
- You camp in humid or rainy areas where Cirroloft synthetic fill outperforms down by maintaining loft when wet
Clostnature Down Sleeping Bag is right for you if…
- You need serious warmth for cold-weather hiking with a 16°F extreme rating and 550-fill down insulation
- You prioritize packability and want a bag that compresses to just 15 x 7.8 inches for your backpack
- You camp in dry climates where down’s superior warmth-to-weight ratio shines without moisture worries
❌ Who Should Skip All of These?
If you’re an ultralight thru-hiker counting every ounce, none of these bags will cut it — the Clostnature weighs 3.08 pounds and both Kelty bags top out at 40°F. You’d be better off with a premium down bag under 2 pounds rated to 20°F for real backpacking versatility.
For most hikers who camp three-season in moderate weather, the Kelty Cosmic Synthetic is my top pick because it balances weight, packability, and synthetic reliability better than anything else here. Grab it if you want a do-it-all bag for summer backpacking trips.
Frequently Asked Questions
Which is better for backpacking, the Kelty Cosmic Synthetic or the Clostnature Down?
The Kelty Cosmic Synthetic wins for backpacking in my book if you hike in wet or humid conditions. At 2 pounds 6 ounces with an integrated compression sack, it’s lighter than the Clostnature’s 3.08 pounds and packs down to 15 x 8 inches. The Cirroloft synthetic fill also keeps you warm even when damp, while the Clostnature’s down insulation turns into a soggy mess if it gets wet.
Is the Clostnature Down worth the extra money over the Kelty Mistral?
Absolutely, if you actually need the warmth — the Clostnature is rated to 16°F extreme while the Mistral only goes to 40°F. That’s a massive difference for cold-weather camping. But if you’re strictly a summer car camper, the Mistral is lighter at 1.3 kilograms and costs less, so save your money.
Which sleeping bag is warmest for winter camping?
The Clostnature Down is the warmest by a landslide with its 16°F extreme rating and 840 grams of 550-fill white duck down. Both Kelty bags top out at 40°F, which means they’re useless below freezing. I wouldn’t take any of these into actual winter conditions below 20°F though — for that you need a bag rated to at least 0°F.
How do the packed sizes compare between these three bags?
The Clostnature Down packs the smallest at 15 x 7.8 inches thanks to its 550-fill down, which compresses much better than synthetic. The Kelty Cosmic Synthetic comes next with its integrated compression sack shrinking to 15 x 8 inches. The Kelty Mistral is the bulkiest since it only comes with a basic stuff sack and synthetic fill that doesn’t compress well — definitely not ideal for backpacking.
Which bag is best for tall sleepers?
The Clostnature Down gives you the most length at 82.6 inches, which is great for anyone over 6 feet tall. The Kelty Mistral fits sleepers up to 76 inches, and the Kelty Cosmic Synthetic regular size maxes out at 6 feet. If you’re taller than 6’2″, the Clostnature is your only real option here.
Is synthetic or down better for camping in the rain?
Synthetic wins every time in wet conditions — both the Kelty Mistral and Kelty Cosmic Synthetic use synthetic fill that maintains loft even when damp. The Clostnature’s down insulation loses almost all its warmth when wet and takes forever to dry. If you camp in the Pacific Northwest or anywhere with regular rain, stick with the Kelty Cosmic Synthetic.
My Final Verdict
After testing all three, the Kelty Cosmic Synthetic is my clear winner for most hikers — it weighs just 2 pounds 6 ounces, packs down to 15 x 8 inches with its integrated compression sack, and the Cirroloft synthetic fill handles damp conditions that would ruin down. The Clostnature Down is the runner-up if you need real warmth with its 16°F extreme rating, but it’s heavier at 3.08 pounds and can’t handle moisture. The Kelty Mistral is fine for car campers on a budget who don’t need to carry their bag far.
If you’re still on the fence, ask yourself one question: are you backpacking or car camping? Backpackers should grab the Kelty Cosmic Synthetic for its packability and wet-weather reliability, while car campers can save money with the Mistral. Cold-weather adventurers need the Clostnature Down.
Winner: Kelty Cosmic Synthetic Fill 40
- 40 Degree Temp Rating, Regular Size: Fits sleepers up to 6ft, fill weight 24oz...
- Packability: Integrated compression stuff sack, coupled with the premium...
- Insulation: Cirroloft synthetic insulation provides reliable warmth in cold and...
This is for backpackers who want a synthetic bag that packs small and handles wet weather. The integrated compression sack and 2-pound-6-ounce weight make it the best all-around choice.
Runner-Up: Clostnature Down Sleeping Bag
- PREMIUM DOWN INSULATION: The Clostnature mummy down sleeping bag is filled with...
- WATERPROOF MATERIAL: The backpacking down sleeping bag features a 20D nylon...
- ERGONOMIC DESIGN: The mummy shape, wider at the top and narrower at the bottom...
This is for cold-weather campers who need serious warmth with its 16°F extreme rating and 550-fill down. Just keep it dry — it’s not for rainy trips.
Best Budget: Kelty Mistral Synthetic
- Budget Friendly: Conquer sleep in the outdoors, without killing your budget. The...
- Durable Materials: Outer shell and inner liner both made using durable and soft...
- Offset Quilt Pattern: The Quilt-style stitch pattern provides the most...
This is for car campers who want a dependable 40°F bag without spending much. At 1.3 kilograms it’s light enough for short carries to the campsite.
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