Therm-a-Rest Boost 650 20F/-6C Down Sleeping Bag, Short Wide — Adjustable Shape & Warmth

Comfort is not a one-size-fits-all proposition, and the Therm-a-Rest Boost 650 sleeping bag is rated to 20F (-6C) with an adjustable shape for customizing warmth. Its spacious semi-rectangular design invites side sleeping, shifting, and relaxing, while a center WarmZip lets you tailor heat and fit on the fly. For backcountry nights that swing between cool and damp, this bag adapts rather than forces you into a single silhouette.

Flexible warmth and shape

WarmZip is a patent-pending center zipper that can reduce the bag’s internal space and wrap insulation around you. When zipped, it converts to a thermally efficient mummy shape that concentrates heat where you need it most. Depending on conditions, this feature can add up to 10 F (6 C) of warmth by reducing the volume your body has to heat.

• Center WarmZip concentrates insulation for extra warmth
• Unzip for more space, ideal for side sleepers and restless nights

Insulation that targets warmth without waste

The Boost 650 uses 650-fill hydrophobic down that’s zoned to keep critical areas warm while saving bulk where it matters least. Hydrophobic down sheds moisture and dries faster, helping you stay comfortable in variable weather.

• Zoned insulation places down at top, core, and shoulders for maximum heat efficiency
• 650-fill down with hydrophobic properties resists dampness

Materials and finish you can feel

The shell and liner are made from 100% recycled nylon that feels soft to the touch. A PFAS-free DWR coating adds a layer of weather resistance without compromising the bag’s feel. The result is a warm bag with a lighter environmental footprint.

• PFAS-free DWR coating reduces environmental impact
• 100% recycled nylon shell and liner feel soft and lightweight

Design details that matter in the field

Two-way side zippers give you venting options from torso to feet, while arm holes allow you to reach the WarmZip without fully opening the bag. For additional comfort, it includes a puff collar, draft tube along the zipper line, and a cinchable hood to seal warmth in drafty nights. Durable YKK anti-snag pulls minimize snags and tears on rough trails.

• Two-way zipper for flexible ventilation
• Arm holes provide easy access to the center zipper while preserving warmth
• YKK anti-snag pulls protect fabrics and zippers from damage

Size, weight, and packability

The Short Wide version provides extra shoulder room and a comfortable fit for those who move around at night. It weighs 2 lb 13 oz (1.27 kg), measures 73 x 37.5 in, and packs down to 10 x 6.5 in. Includes a storage bag and compression stuff sack for compact transport.

With inclusive sizing and thoughtful warmth zoning, the Boost 650 is built for backpacking in variable backcountry conditions. It offers space to breathe and rest without promising guaranteed outcomes, leaving room for your personal comfort preferences on every trip.