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The Therm-a-Rest Boost 650 is a semi-rectangular down sleeping bag rated to 32F/0C that converts to a mummy shape with a WarmZip center zipper. That zipper pulls the 650-fill hydrophobic down close to your body and Therm-a-Rest claims it adds up to 10F/6C of warmth. Arm holes let you reach gear, read or vent without opening the side zipper. It suits campers who want room to move and sleep in any position but still want a bag that can tighten down on cold nights. Against a plain mummy bag it trades some weight and packed size for space and flexibility; against a pure rectangular bag it insulates better and packs smaller. Owners rate it highly for comfort and the WarmZip design.
Availability unknown
Lowest price we've seen: $249.99 on Nov 5 at Bill & Paul's Sporthaus. Tracked across 1 store since Nov 5.
Owners rate the Boost 650 very highly, with 4.8 out of 5 from 111 ratings. They praise the roomy semi-rectangular shape, the WarmZip conversion and the arm holes. The main complaints are weight and packed size versus a mummy bag.
The Therm-a-Rest Boost 650 is a 32F/0C sleeping bag in a Regular Wide size, made for backpacking and car camping. Its semi-rectangular shape gives more internal space than a mummy bag, so you can sleep in whatever position you like.
A WarmZip center zipper changes the bag into a thermally efficient mummy shape. It pulls the 650-fill down around your body and reduces the space your body has to heat. Zipping it up can add up to 10F/6C to the temperature rating.
Arm holes give access to the WarmZip and to your belongings without using the side zipper. They can also be used to ventilate. A two-way side zipper lets you vent around the torso or at the feet. Every zipper line has a YKK anti-snag pull.
