Kelty

Cosmic Synthetic 40

Kelty Cosmic Synthetic 40

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Overall

#229 in

Outdoor Sleeping Bags

according to Reddit Icon Reddit

Sentiment score50% positive
2
1
1
Last updated: May 19, 2026

Reddit Reviews

Reddit IconJamal_Tstone
7 months ago

I've been tent camping for a while now, and I thought I'd try bushcraft. Now I haven't gone the whole 9 yards with a wool blanket and sleeping on the ground, but I am using a tarp shelter. Specifically, I had a Nemo Tensor and a Kelty Cosmic 40°F bag. The temps were forecast down into the 40's, and I just got done using this bag in Alaska where it did just fine in similar temps. 2 things I failed to consider: the tarp being open to the elements and the humidity. It's been raining for days, and this was the first clear weekend. Needless to say, I was too cold to get quality sleep so I packed up and headed out, but I went out there on a motorcycle and didn't bring sufficient clothes for riding in anything other than warm daylight. The wind chill of going 60mph damn near froze me solid. I had to pull over on the side of the road and thaw myself out multiple times on the way home. Lessons learned!

Reddit IconLetMany4907
7 months ago

For casual three-season camping around 0°C, synthetic’s way easier on the wallet. Marmot Trestles or Kelty Cosmic Down alternative bags hold up fine, and you don’t freak out about melting water or sweat ruining insulation.

Reddit IconVote_Knope_2020
11 months ago

I have the single version of this and also love it. Super versatile temp-wise.

Reddit Iconajhejunk
Reddit Iconcwcoleman
5 months ago

Can you add more specific details? You have this labeled as 'travel' - but ask about camping gear. I assume you are asking about the 'wilderness' type of backpacking - right? What is the low temps you plan to sleep in? You say no snow - but 'colder temps' - a number would help. What is your budget? Do you have $500 to spend? $5000? You say 'wreck bank account - but everyone's bank account is different size. How old are you? Man or Woman? (many packs and sleeping bags are gendered) Do you already have a good sleeping pad? This is also critical to a good / warm night sleep. Do you already have a tent? Sure - Kelty is a find budget getting started brand. They make an okay Cosmic down sleeping bag that's popular for wilderness backpacking. I wouldn't go for their backpacks really. Here are some default recommendations from Amazon: * [https://www.amazon.com/Kelty-Sleeping-Backpacking-Recycled-PFAS-free/dp/B0CSPFW5Q1](https://www.amazon.com/Kelty-Sleeping-Backpacking-Recycled-PFAS-free/dp/B0CSPFW5Q1) * [https://www.amazon.com/Osprey-Atmos-Backpacking-Backpack-X-Large/dp/B09JXQDZG5](https://www.amazon.com/Osprey-Atmos-Backpacking-Backpack-X-Large/dp/B09JXQDZG5) * [https://www.amazon.com/Therm-Rest-Original-Ultralight-Camping/dp/B00453NA1E](https://www.amazon.com/Therm-Rest-Original-Ultralight-Camping/dp/B00453NA1E) * [https://www.amazon.com/Therm-Rest-Ultralight-Backpacking-Sleeping/dp/B0CS4NHPVP](https://www.amazon.com/Therm-Rest-Ultralight-Backpacking-Sleeping/dp/B0CS4NHPVP)

Reddit Icongmxrhythm
12 months ago

Then I'd say the new REI Radiant 20. It's a mostly down bag, but with synthetic in the footbox to accommodate sweat and if it gets wet in the night from rain (because most people stretch out and end up putting their feet against the tent wall which might have condensed). The Kelty Cosmic is a close second.

Reddit IconInternConnect6963
9 months ago

Kelly cosmic down bags are amazing bang for buck. REI has generous return policies as well, so if you get into a bag you don’t like, you have the option to return it for a year. More expensive bags/huge discounts don’t necessarily mean they are going to fit your needs. I currently sleep in the Big Agnes Lost Ranger, which is a 3in1 sleep setup. It is a quilt and a sleeping bag, which means you can sleep with just the quilt, just the bag, or if it’s cold enough you can nest the sleeping bag inside the quilt. It’s on the more expensive side, but it could be beneficial looking into a similar setup. I would however recommend investing in a nice sleeping pad that has a decent R value. I currently sleep on the Big Agnes Rapide SL Insulated (regular) and I LOVE IT. it comes in all different types of widths and lengths. I’ve slept on it for 2+ weeks in the Yosemite side country and I’ve never had a single issue with it. long story short, i’m a huge fan of the Kelty Cosmic Down line. there are also a few REI branded bags that may be worth looking at.

Reddit IconStapledOK
9 months ago

Can def get closer to 2 for a little more money. Kelty cosmic or REI brand stuff on sale. Down is much lighter than synthetic. Quilts are also an option...

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