Thermarest - Boost 650 32F/0C Sleeping Bag

Getting a solid sleep in the backcountry starts with a bag that fits the way you actually sleep, and the Therm-a-Rest Boost 650 was built around exactly that idea. The standout feature here is WarmZip, a centre zipper that lets you toggle between a roomy semi-rectangular shape and a thermally efficient mummy configuration. Zip it up and you pull 650-fill hydrophobic down in tighter around your core, adding up to 10°F/6°C of warmth without swapping bags.

The arm holes are genuinely clever. Reach your WarmZip, grab a snack, flip through a book, or just stick your arms out if you're running warm, all without climbing out of your bag. A two-way side zipper adds another layer of ventilation control, so you can dial in comfort from your torso to your feet. YKK anti-snag pulls on every zipper keep things frustration-free in the dark.

For a bag this comfortable, the packability is impressive. Zoned Insulation puts the down where it counts most, on top and around your shoulders and core, and scales it back underneath where your sleeping pad handles the work. The shell and liner are GRS-certified 100% recycled nylon with a PFAS-free DWR coating, keeping things light, soft, and weather-resilient. Available in Small, Regular, and Long, each with a Wide option for a genuinely good fit.

• Fill: 650-fill RDS-certified hydrophobic down
• WarmZip adds up to 10°F/6°C to temperature rating
• Shell and liner: GRS-certified 100% recycled nylon
• PFAS-free DWR water-repellent coating
• Zoned Insulation for targeted warmth efficiency
• Two-way side zipper with YKK anti-snag pulls
• Features: cinchable hood, draft collar, zipper draft tube, arm holes
• Sizing: Small, Regular, Long (all available in Wide)
• Includes compression sack and storage sack