Kelty
Cosmic Synthetic 40 Degree
Best comfortable and reliable synthetic sleeping bag for budget conscious adventurers.
Designed for three-season backpacking, this mummy bag balances lightweight performance with reliable warmth. It utilizes advanced synthetic insulation that remains effective even in damp conditions, ensuring comfort throughout the night. The spacious footbox allows for natural movement, while the soft-touch fabrics provide a comfortable sleeping environment. Featuring a convenient integrated pocket for small essentials and a durable, water-repellent finish, this bag is built to handle the rigors of the trail. It offers an accessible entry point for hikers seeking a dependable, compressible sleep system without the bulk or maintenance requirements of traditional down insulation.
$99.95
More Cosmic Options
Cosmic 20
$159.95
Cosmic Down 20
$189.95
Cosmic Synthetic 0 Degree
$139.95
Cosmic 20 Degree Sleeping Bag
$159.95
Cosmic Ultra 20 Degree
$269.95
Cosmic
$314.95
Cosmic 20 Sleeping Bag (Long)
$109.95
Cosmic Synthetic 20 Degree
$119.95
Cosmic 40
$119.95
Cosmic Synthetic 20
$109.95
Cosmic 20 Sleeping Bag
$118.22
Cosmic Ultra 0°F Sleeping Bag
$219.95
Cosmic Ultra 800 DriDown Sleeping Bag
$184.48
Cosmic 0 Synthetic Sleeping Bag
$129.95
Cosmic 20 Sleeping Bag
$118.22
Cosmic Ultra 0°F
$245.97
Kelty Cosmic 20
$169.99
Kelty Cosmic Synthetic 0 Degree Sleeping Bag
$166.00
Kelty Cosmic Down 20
$189.95
Kelty Cosmic Ultra 0
$369.95
Cosmic Synthetic 20
$109.95
Owner Satisfaction
4.5
/ 5
Category Rank
1010
/ 2020
#1010 in Sleeping Bags
Price vs Category Average
-40%
Below average
ISO Comfort Temp Rating
373
/ °F / °C
Who it's for
- Campers in humid climates or those prone to damp gear.
- Budget-conscious adventurers seeking reliable gear without breaking the bank.
- Recreational campers enjoying mild weather and car camping adventures.
Who should skip it
- Backpackers needing a versatile bag for three-season or colder conditions.
- Ultralight backpackers prioritizing minimal weight and pack volume.
- Long-term users expecting maximum durability and consistent warmth for years.
Performance breakdown
Moisture Resilience
Synthetic insulation maintains loft and warmth even in damp, humid conditions.
Weight-to-Warmth Ratio
Solid thermal efficiency, though heavier than premium down alternatives.
Footbox Comfort
Natural-fit design provides ample room for toes to move freely.
Packability
Synthetic fill requires more space in your pack than down counterparts.
Fabric Durability
Tough nylon shell stands up well to frequent trail use.
Temperature Versatility
Reliable three-season performance for mild to cool backpacking nights.
Key Specs
ISO Comfort Temp Rating
37°F / 3°C
ISO Limit Temp Rating
27°F / -3°C
Fits to
6 feet / 183 cm
Length
78 inches / 198 cm
Shoulder Width
31 inches / 78.5 cm
Fill Weight
26.5 oz / 0.75 kg
Total Weight
2.68 lbs / 1.22 kg
Stuffed Size
15 x 8.5 inches / 38 x 22 cm
Know before you buy
The Cosmic Synthetic 40 is rated for a comfort temperature of 37°F (3°C) and a limit rating of 27°F (-3°C). It is designed primarily for three-season backpacking, making it a reliable choice for spring, summer, and early autumn trips.
This bag uses CirroLoft synthetic insulation, which is heavier and bulkier than down but performs significantly better in damp or humid conditions. Unlike down, which loses its loft and warmth when wet, synthetic insulation retains its thermal properties even if it gets moist.
Yes, the bag is designed to fit users up to 6 feet (183 cm) tall. The total length of the bag is 78 inches, providing enough room for a comfortable fit at that height.
Yes, the shell features a PFC-Free DWR (Durable Water Repellent) coating. While it is not waterproof, this finish helps shed light moisture and condensation, protecting the insulation from getting soaked.
The natural-fit footbox is shaped to allow your feet to rest in a more relaxed, upright position rather than forcing them into a pointed orientation. This extra space prevents the insulation from being compressed by your toes, which helps keep your feet warmer throughout the night.
No, this model does not include a draft collar. It relies on a standard mummy hood design to retain heat, which is typical for a bag in this temperature rating and weight class.
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$100