Therm-a-Rest Boost 650 20F/-6C Down Sleeping Bag, Large Wide | Adjustable Shape for Comfort

Adaptive comfort for real-world sleep on the move

The Therm-a-Rest Boost 650 is designed to fit how you actually sleep. Its roomy semi-rectangular form gives you space to roll onto a side, stretch out, or shift during the night. When conditions change or you crave a leaner profile, the built-in WarmZip center zipper tucks insulation around you and narrows the internal chamber, transforming the bag into a warmer mummy shape without removing any layers. This clever adjustability means you can fine-tune warmth and space to match the night, rather than squeezing into a one-size-fits-all bag.

Key warmth comes from thoughtful insulation placement. The 650-fill hydrophobic down is prioritized around the top, core, and shoulders while tapering towards the bottom, creating more warmth where you need it most without adding unnecessary weight. The result is a balanced blend of heat retention and packability that appeals to backpackers who value versatility as much as comfort. The shell and liner are made from 100% recycled nylon with a PFAS-free DWR, blending performance with a lighter environmental footprint.

Smart design details to boost warmth and ease

• WarmZip center zipper can reduce internal space and boost warmth by up to 10°F (6°C) in suitable conditions.
• Inclusive sizing includes Wide options for broader shoulders and restless sleepers, plus a centered zipper for balanced fit.
• Easy arm access with multi-use arm holes—reach, sip a drink, or stay warm without breaking the seal.
• Two-way side zipper allows ventilation or partial entry without compromising warmth.
• Durable hardware YKK anti-snag pulls reduce snags and tears over time.
• Hydrophobic down helps keep you comfortable in damp conditions.
• Lightweight and packable design tailored for backpacking with a compact pack size.
• Materials you can feel good about 100% recycled nylon shell/liner with PFAS-free DWR for a softer touch and lower environmental impact.

Size, weight, and packing

The Boost 650 in Long Wide weighs about 3 lb 13 oz (1.74 kg) and measures 85 × 38.5 in (216 × 98 cm). It packs down to roughly 14.5 × 7.5 in (37 × 19 cm) and comes with a storage bag and compression stuff sack, making it a practical choice for hikers and travelers who value space efficiency without sacrificing warmth.

Whether you’re pitching in alpine camps, coastal mist, or backcountry bivouacs, the Boost 650 offers a flexible sleep experience. Its combination of warmth, adjustability, and responsible materials supports a broad range of adventures without promising guaranteed outcomes—use it as a possibility rather than a guarantee, and tailor it to your night.