What Our Gearhead(R) Experts Are Saying:"This bag is perfect for anyone who wants warmth without compromise. The WarmZip feature is amazing-it keeps me cozy on cold nights, but I can unzip for more space on warmer evenings. The arm holes are a game-changer for livability. Lightweight and packable, it's my go-to for all my three-season trips."Whether we're under the stars or tucked away in a tent, the Therm-a-Rest Boost 650 Sleeping Bag is our ultimate companion for comfort. Its semi-rectangular design provides spacious freedom for restless sleepers, while the innovative WarmZip system allows us to transform it into a mummy bag when temperatures drop, boosting warmth by up to 10degF. Perfectly balancing plush comfort and packable performance, the Boost features 650-fill RDS-certified hydrophobic down, strategically zoned to maximize warmth where we need it most. The eco-conscious shell and liner, made from 100% recycled nylon, are coated with PFAS-free water repellent for reliable coziness even in damp conditions. From its multi-use arm holes for easy access to its puffy draft collar and two-way zippers, every detail of the Boost 650 is designed for blissful nights and seamless mornings in the backcountry. Lightweight and versatile, it's ready for backpacking treks, car camping adventures, and everything in between.