NEMO Sonic -20 Sleeping Bag

This product is not available.

Shop similar products

Built to be the only bag you need from -20°F to 40°F, the NEMO Sonic -20 sleeping bag is warmer and more fine-tuneable than ever before. Time to start planning some big-mountain adventures.


  • Updated Thermo-Gills™ feature a multi-stage zipper system that increases the bag's usable temperature range and allows you to fine-tune your comfort while inside it
  • Chevron baffle construction better compartmentalizes down, eliminating migration and keeping the down evenly lofted
  • Upgrades include a redesigned profile and draft collar, plus bolstered draft tubes; offset zipper creates a thermally efficient seal
  • Shell and liner fabrics are fully recycled to the Global Recycled Standard (GRS)
  • Shell and liner materials are bluesign® approved
  • 800-fill-power, PFC-free hydrophobic down retains warmth in extra-cold conditions
  • Down is certified to the Responsible Down Standard (RDS)
  • Toester™ footbox keeps feet warmer, provides a waterproof barrier against tent wall condensation and protects down from moisture while drying damp clothes inside the footbox
  • Stretch construction at the knees allows for comfortable side sleeping
  • Covered by the NEMO Lifetime Warranty


Many sleeping bags are rated for temperature by an independent testing protocol. REI and the broader industry now use the International Organization for Standardization (ISO) 23537 protocol, which improves on the older European Norm (EN) 13537 standard; you may still see older items in our assortment that were only EN tested. With either protocol, each bag gets a Comfort (or T-Comfort) rating and Lower Limit (or T-Limit) rating. The Comfort rating is the lowest temperature at which the bag will keep the average "cold sleeper" comfortable, and the Lower Limit rating is the lowest temperature at which the bag will keep the average "warm sleeper" comfortable. Ratings are based on a person wearing one long underwear layer and a pair of socks, sleeping on an insulated surface with a minimum R-value of 5.38. Many brands use the Comfort rating for women's bags and the Lower Limit rating for men's and unisex bags. Everyone's body and sleep comfort differ, and conditions of use (posture, clothing, sleeping pad R-value, wind, humidity, etc.) affect total insulation, so EN and ISO ratings are intended as a guideline to help you compare products, rather than a guarantee of warmth.
View all NEMO Backpacking Sleeping Bags

Technical Specs

Best Use



Tested Lower Limit

-20 degrees (F) - ISO

Tested Comfort


Temperature Rating (F)

-20 degrees (F)

Temperature Rating (C)

-29 degrees (C)


Recycled nylon

Zipper Location


Insulation Type


Water-Resistant Down



800-fill-power down


Recycled polyester

Sleeping Bag Shape


Shoulder Girth (in.)

63 inches

Hip Girth (in.)

58 inches




Product meets the bluesign® criteria

9 reviews with an average rating of 3.9 out of 5 stars

Loading Reviews...

Questions & Answers

Loading Questions...