About the Cosmic Down 20

Remember the trapezoid from high school geometry? Turns out, this funky ol' shape is ideal for helping sleeping bags retain heat. Our trapezoidal baffle construction is just one of the reasons the Cosmic Down is still our favorite three-season superstar. We also love the expanded natural-fit footbox for happier feet, zippered stash pocket and fully recycled fabrics and PFAS-free DWR treatment. The Cosmic Down is the total package.

PRODUCT SKU - 35413724

Features

• Trapezoidal baffle construction provides enhanced thermal efficiency
• Lofty, lightweight and warm 550 Fill Down
• Buttery-soft and durable, fully-recycled shell and liner fabrics with PFAS-free DWR
• Zippered internal stash pocket keeps your favorite devices close at hand
• Full draft tube and collar retain heat and enhance comfort
• Quad-stitch anti-snag zipper makes getting in and out easy
• Dual locking sliders for venting versatility
• Expanded, natural fit footbox = more room to wiggle your toes
• Stuff sack included, for quick and easy departures

Understanding the Temperature Rating & Sleep System

What the 20°F / -7°C rating means
Kelty rates the Cosmic Down 20 using the EN 13537 / ISO 23537 standard — the same lab-tested protocol used across the outdoor industry for consistent bag-to-bag comparison. Under this standard, three values are established:

• Comfort rating (woman): ~32°F / 0°C — the temperature at which a standard cold sleeper can expect a comfortable night's rest in a relaxed posture.
• Lower Limit rating (man): 20°F / -7°C — the temperature at which a standard warm sleeper can sleep curled up without waking from cold. This is the figure Kelty markets as the bag's rating.
• Extreme rating: ~-4°F / -20°C — a survival threshold only; sustained sleep at this temperature is not expected to be comfortable.

Tested sleep system
EN/ISO ratings are conducted with the sleeper on a thermal insulation mat (R-value 2.0 / ISO value ~0.5 m²K/W). A sleeping mat is therefore required to achieve the stated rating — without one, cold from the ground will compress the bag's down beneath you and significantly reduce warmth. For cold-weather camping, a mat with an R-value of 3.0 or higher is recommended.

Personal cold sensitivity & insulation quality
Real-world comfort varies from the lab figure. Factors that affect how warm you sleep include:

• Metabolism & sleep style — cold sleepers may find the comfort threshold is closer to 32°F / 0°C rather than the lower limit figure.
• Fill power — the Cosmic Down uses 550-fill down. Higher fill-power down (e.g. 800+) lofts more per gram; at the same weight this bag prioritises value over ultralight performance.
• Moisture & humidity — damp down loses loft rapidly. Keep the bag dry and store it uncompressed when not in use.
• Layering — wearing a baselayer, hat and socks inside the bag can add several degrees of effective warmth.

When to choose a warmer bag
Consider stepping up to a lower-rated bag (e.g. 0°F / -18°C) if you: camp regularly at or below 20°F / -7°C, identify as a cold sleeper, plan high-altitude or winter trips, or cannot use a high-R-value mat. The Cosmic Down 20 is best suited as a three-season bag for conditions down to its lower limit rating with an appropriate mat.

Specifications