Kelty Cosmic Ultra 20 Review

Bottom Line

The Kelty Cosmic Ultra 20 is one of the best value sleeping bags out there when it comes to comfort, durability, and features. Gear analyst Ian Krammer has thoroughly tested this bag from late winter until mid-summer over 20 nights in the Rocky Mountains The Cosmic Ultra 20 excels with its 800-fill-power insulation and thicker 20-denier nylon shell offers a level of durability that most backpacking bags can only dream of. And this bag is feature loaded, including a large zippered stash pocket, decent sized draft collar, and soft material.

That said, the Cosmic Ultra 20 is among the heavier options we’ve tested. While it represents an awesome value for budget-conscious shoppers, it’s not the warmest bag out there and it doesn’t pack down as small as ultralight options, but it’s excellent for summer and warm weather. However, if price tag and performance are top of mind, the Cosmic Ultra 20 is a compelling and cozy bag for adventurers of all skill levels.

Warmth

The Cosmic Ultra 20 is warm enough for temperatures down to 35°F. Its trapezoidal baffle construction and long draft tube work together to keep heat trapped inside, meaning you’ll stay warm on those cool mountain or desert nights. Its 800-fill-power Dridown offers extra water-resistance that thrives in wet conditions and humid climates, since it dries so quickly if the bag gets wet from weather or condensation. 

The 20-denier fabric is much more robust and insulating compared to the thinner 10D and 15D fabrics used in many ultralight bags, and makes the Cosmic Down feel warmer while adding significant durability. Although the draft tubes are somewhat minimalist and not as wide or filled with down as other bags we tested, they effectively retain warmth, cover the zippers, and block drafts when the colder temperatures settle in.

The downside of the Kelty Cosmic Down is, in our experience, the comfort rating is overstated. Gear Analyst Ian Krammer found that after five nights in 25°F temperatures, the bag struggled to keep him warm, even while he was wearing a base layer and the bag was paired with a sleeping pad with a 5 R-value. We would recommend this bag for overnight temperatures between 35°F and 65°F. 

And, we wish the Cosmic Down had narrower baffles. After 15 – 20 uses, we found the down in those wide baffles migrated toward the edges and corners instead of staying spread out evenly across the bag. To fix this, we had to either manually massage the down back into place, or wash and dry the bag more often to re-distribute the down.

Comfort

The Kelty Cosmic Ultra 20 is a cozy backcountry bag. Kelty uses a luxurious, thick, and burly 20D nylon for the shell and liner of this bag that feel super soft against the skin, and is a pleasure to slide into after a long day of hiking. The 800-fill-power Dridown insulation means this bag feels plenty warm, but offers stellar water-resistant and fast-drying properties – perfect for backpacking on rainy days and in damp climates. We’re big fans of the larger footbox that easily accommodates most sleeping positions. And, the versatility of a mummy bag design is always a win for comfort: cinch the hood tightly and snuggle into the bag on chilly nights, or unzip the entire bag for partial coverage on warm evenings. It’s comfortable to carry, too, since the included stuff sack packs it down to a manageable size for long miles on trail.

On the downside, this bag doesn’t have much of a shape to it and lacks body contouring. That directly translates to a less snug fit than other competitive mummy bags.Many people will appreciate this, but for folks who like and want a snugger sleep system, this bag might not be a great fit. And, the mummy hood will definitely fit your head, but it is much smaller compared to competitive bags, so it’s a challenge to fit a backpacking pillow comfortably inside.

Weight & Packability

Weighing 2 pounds, 5.6 ounces for the regular size and 2 pounds, 14 ounces for the long size, the Cosmic Ultra 20 is heavier than the ultralight options we tested and also has a lower warmth-to-weight ratio. But, don’t let that stop you – this is still an outstanding weight for short and moderate backpacking trips! We’ve trekked hundreds of miles with this sleeping bag and didn’t think twice about the weight – plus, the bag remains highly packable and easy to carry. If weight is a concern but staying within budget is crucial, consider complementing the bag with a lightweight sleeping pad to balance the weight. 

The benefit of a slightly heavier weight? Awesome durability and one of the most feature-rich backpacking sleeping bags on our list. A thick 20-denier nylon shell contributes to the heft of the Cosmic Down. Sure, it’s a bit bulky to store and carry, but its lifespan is longer than the thin 10D and 15D fabrics used in many other bags. That means a longer-lasting product. The bag’s bulk might be a drawback for ultralight hikers, but its affordability and durability make it a strong contender for folks seeking a high-quality, cost-effective option.

Features

This is one of the most feature-rich down bags on our list. Unlike many pricier, minimalist options, it has a zippered internal stash pocket perfect for storing a cell phone, headlamp, or chapstick. The anti-snag zipper is one of the smoothest in the game, and rarely snags on the material when entering or exiting the bag. The bag includes a stuff sack that makes packing up easy, although Kelty doesn’t include a mesh storage sack to maintain the bag’s loft when it’s not in use. The snug hood is essential for excellent coverage and warmth, making the Cosmic Down suitable into the low 40s and upper 30s, and we like that the cinching mechanism is easy to access from inside and outside.

Our only complaints come down to the design of certain features. The draft tube, though functional, is a bit flimsy and underfilled compared to other high-end models, so it’s not as effective at blocking cold drafts and retaining warmth. And, the hood is small, so it’s not as compatible with backpacking pillows. That said, at this price and high-caliber quality, we think the Cosmic Down is an awesome bag for beginners or budget-conscious backpackers who want the full spectrum of features without breaking the bank.

Should You Buy the Kelty Cosmic Ultra 20?

The Kelty Cosmic Ultra 20 is our top choice for budget-conscious backpackers and beginners who need a reliable, durable sleeping bag without spending a fortune. Its 800-fill-power Dridown insulation and beefy 20-denier nylon shell offer excellent warmth and durability, so it’s a great bag for everything from base camps in high alpine environments to week-long thru-hikes in the desert. Features like a zippered internal stash pocket, anti-snag zipper, and a spacious footbox make this model feel über comfy and functional.

However, ultralight hikers and long-distance backpackers who want the lowest weight sleeping bag will want to keep shopping. Its bulkier design and heavier weight compared to other models will be less appealing if you’re counting every ounce and gram and want the smallest sleeping bag out there. Also, the absence of a mesh storage sack and the somewhat flimsy draft tube could impact performance in very cold conditions.

What Other Backpacking Sleeping Bags Should You Consider?

NEMO Disco 15 Endless Promise Review: The NEMO Disco 15 Endless Promise, like the Kelty Cosmic Ultra 20, offers a similar temperature rating, a spacious footbox, and lots of features. However, it stands out for its unique Spoon Shape design, which is more comfortable for different sleeping positions and is only a bit heavier.

REI Magma 15 Review: The REI Magma 15, similar to the Kelty Cosmic Ultra 20, features high-quality down insulation, fill power, and overall weight. It may be a better option if you’re looking for a more packable, warm, and slightly roomy option, as long as you’re willing to pay more for it.

Marmot Trestles Elite Eco Review: The Marmot Trestles Elite Eco is similar when it comes to weight, warmth, and durability. But, if you’re looking for a bag with synthetic insulation that dries very fast and costs significantly less – with the same reliable performance and features – the Trestles Elite Eco is an awesome alternative.