Nemo Equipment Sonic Down Sleeping Bag

The Thermo-Gills are essentially zippered vents located along the chest area. By unzipping them, you can dump excess body heat without letting in a draft, allowing you to use the bag comfortably in temperatures up to 40°F without overheating.

Yes, this bag is designed specifically for winter conditions. The 800-fill hydrophobic down provides excellent loft, and the chevron baffle construction keeps that insulation evenly distributed so you don't end up with cold spots.

The footbox is designed with a waterproof barrier to protect your feet from condensation that often accumulates at the bottom of a tent. It also provides a bit of extra space to stash damp socks or gear you want to dry out overnight.

Yes, Nemo prioritized sustainability with this model. Both the shell and liner fabrics are 100% GRS-certified recycled materials, and the entire bag is bluesign approved, meaning it meets strict environmental and chemical safety standards.

The short version weighs 3.125 lbs and compresses down to 8.9 liters. While it is a robust winter bag, it packs down reasonably well for its warmth rating, making it manageable for backcountry trips where space is at a premium.

While it is a mummy shape, which is necessary for thermal efficiency in winter, the bag is designed to balance warmth with mobility. If you are a restless sleeper, you may find it slightly more confining than a rectangular bag, but it is standard for a high-performance winter sleeping system.