Sonic™ Down Mummy Sleeping Bag

$448.77 ~~$679.95~~ In stock

Category: Men's Mountaineering Sleeping Bags

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.

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Customer Reviews (5.0 / 5 · 5 reviews)

James X. ★★★★★ Aug 22, 2026

Took this out in single-digit temps and the draft collar plus hood cinch kept every bit of warmth locked in, even when the wind picked up. The temperature range is no joke—I unzipped it halfway at 35°F and was perfectly comfortable. It's lighter than my old bag by a good margin, which makes the moun

Lucy G. ★★★★★ Aug 21, 2026

Backed up the claim about the temperature range on a single-digit night in the alpine, and the draft collar sealed everything in so well I actually had to unzip the foot vent by morning. The 40°F end is a stretch for me, but from 20°F down it's dead-on.

Scarlett ★★★★★ Aug 20, 2026

The draft collar cinched down without any gaps, so even at 15°F I wasn't fishing for a hood opening in the dark. The draft collar really locks in heat when I move around at night.