Sonic™ Down Mummy Sleeping Bag -20F / -29C


SKU: 268632

Sonic is built to be the only bag you need from -20°F to 40°F. The Backpacker Editors’ Choice award-winning big-mountain bag offers exceptional warmth and tuneability with a reduced environmental impact. This bag features our next-generation Thermo Gill™ vents, with a new multistage zipper system that dramatically increases the usable temperature range of the bag and allows fine-tuning of comfort from within. Sonic’s chevron baffle construction better compartmentalizes down, eliminating migration and keeping the down evenly lofted. (Not to mention, it looks awesome.)

The shell and liner fabrics are 100% recycled fabrics and bluesign® approved, and the premium 800 FP hydrophobic down is 100% Responsible Down Standard (RDS) certified. Years of history in the field yielded detailed upgrades on this bag, including a perfected profile, redesigned draft collar, and bolstered draft tubes. Our proven 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. Adaptable to whatever the mountain throws at it, Sonic continues to reverberate as the ultimate extreme weather companion.


  • Thermo Gill™ vents allow for temperature regulation in variable mountain climates without letting cold air in.
  • Premium materials such as a 20D nylon ripstop shell and a smooth 30D nylon taffeta on the interior increase durability and comfort.
  • Stretch construction at the knees allows side sleeping.
  • Stuffed with 800 FP hydrophobic down that is 100% RDS-certified. Products certified to the Responsible Down Standard (RDS) contain down or feathers from farms certified to animal welfare requirements.
  • Down-filled draft collar and draft tubes create a secure seal to keep cold air out.
  • Toester™ waterproof/breathable footbox relies on an additional layer of synthetic insulation to reduce cold spots.
  • Offset zipper creates a thermally efficient seal.
  • Contoured profile secures warmth closer to the body.
  • Protected by the NEMO Lifetime Warranty.


Capacity 1 Person
Minimum Weight 3 lb, 14 oz / 1.76 kg
Packed Size 14.5 x 10.5 in dia / 37 x 27 cm dia
Temp Rating -20F / -29C
Fill Type 800 FP Down
Fill Weight 2 lb, 5 oz / 1.06 kg
Fits Up To 6' / 183 cm
Shoulder Girth 63 in / 160 cm
Hip Girth 58 in / 147 cm
Knee Girth 53 in / 135 cm
Compressed Volume 9.6
Shell Fabric 100% Recycled Nylon, Bluesign Certified
Footbox Fabric 100% Recycled Nylon, Bluesign Certified
Lining Fabric 100% Recycled Polyester, Bluesign Certified
Color Goodnight Gray / Torch
Zipper Location Left
Stuff Sack Compression stuff sack
Insulation Down