Therm-a-Rest Boost 650 20F Sleeping Bag

A three-season sleeping bag that solves the longstanding tension between comfort and thermal efficiency. The Boost 650 gives you the spacious, unrestricted feel of a semi-rectangular bag when you want it and the warmth of a mummy bag when you need it, all with a single zip.

Highlights

• WarmZip center zipper system — A patent-pending center zipper that transforms the bag from semi-rectangular to mummy shape in seconds. Adds up to 10°F of warmth by pulling insulation around your body and reducing the space your body needs to heat. Two bags in one without carrying two bags.
• Semi-rectangular default shape — Significantly more internal space than a standard mummy bag for side sleepers, restless sleepers, and anyone who finds traditional mummy bags claustrophobic. Enough room to shift position freely through the night.
• Arm holes for elevated livability — Access the WarmZip, read, eat, or reach your gear without unzipping the bag or losing warmth. Ventilate when you're too warm without fully exposing yourself to cold air. A feature that changes how you interact with your sleeping bag at camp.
• 650-fill RDS-certified hydrophobic down with Zoned Insulation — Down is concentrated where it matters most for warmth retention, on top and around the core and shoulders, and reduced on the bottom where compression eliminates its effectiveness anyway. More warmth with less material.
• PFAS-free DWR with hydrophobic down — Weather-resistant treatment and moisture-resistant down work together to maintain warmth in damp conditions without forever chemicals in the finish.
• 100% recycled GRS-certified nylon shell and liner — Lightweight, super-soft, and sustainably sourced. A material choice that holds up to repeated use without sacrificing comfort against the skin.
• Two-way entry zipper with YKK anti-snag pulls — Ventilate at the torso or the feet independently. Every zipper on the bag runs smoothly without catching or tearing insulation.
• Cinchable hood, draft collar, and draft tube — A full thermal seal package that eliminates cold spots at the head, neck, and zipper line on cold nights.
• Available in Short, Regular, and Long in standard and Wide widths — A sizing range that actually fits different body types rather than forcing everyone into the same bag shape.
• Compression sack and storage sack included — Pack it down for the trail and store it properly at home to preserve loft over the long term.

Best for

Three-season backpackers and campers who want a comfortable, versatile sleeping bag that adapts to variable conditions and different sleeping styles without requiring a separate bag for cold nights. A strong choice for anyone who has compromised on either comfort or warmth in a sleeping bag and is ready to stop.