What Our Gearhead(R) Experts Are Saying:"The Mad River 40 is my go-to sleeping bag for warm-weather backpacking. It's lightweight, packs down small, and the 650-fill ExpeDRY down stays lofty even in humid conditions. The dual-zipper design makes it easy to vent on hot nights, and the draft collar helps keep warmth in when temperatures dip. It's comfortable, breathable, and perfect for summer nights on the trail."For warm summer nights in the backcountry, the Marmot Mad River 40 Sleeping Bag offers lightweight comfort without unnecessary bulk. Packed with 650-fill-power ExpeDRY down, this bag delivers high-loft warmth while drying quickly in humid or damp conditions. The fully recycled nylon shell and lining reduce environmental impact, making it a sustainable choice for eco-conscious adventurers. Designed for versatility, the full-length snag-free zipper allows for easy entry and exit, while the short right-side zipper provides extra ventilation on warmer nights. The draft collar adds warmth when the temperature drops, and the anatomically wrapped footbox keeps feet cozy without feeling restrictive. Whether we're cowboy camping under the stars or setting up in a breezy tent, the Mad River 40 offers the perfect blend of comfort, packability, and sustainability for summer adventures.